Sometimes you're handling the main quest and a game will throw in some sort of diversion for your entertainment. This minigame, sidequest, or secondary story is so absolutely addictive, interesting, or just plain fun that you'll completely forget about the main story altogether. Don't worry too much about it. This isn't absolutely limited to video games either. Many websites have so many nifty things going on that you don't even care about the main site at all. These are times when the main story or quest gets derailed by what you can do on the side.
Related to Attention Deficit... Ooh, Shiny!. See also Just One More Level and Quicksand Box. It will normally happen in the Minigame Zone. A Virtual Paper Doll, particularly one with a lot of customization options, can easily become one of these if you're the sort of player who cares about that. Compare and contrast Plot Detour where this is the content.
Matrim Cauthon in the Wheel of Time often stops to gamble, infuriating many of his traveling companions, especially the Aes Sedai, especially Aes Sedai protagonists. However, due to his Luck, it might be more accurate to call it fundraising for his paramilitary organization, which is how he often sees it.
The snowboarding minigame became so popular that a cellphone-only version of the game was released in North America and later in Japan.
Saving the world can wait through several generations of Chocobo breeding and racing.
While you're at it, go ahead and slaughter thousands of monsters to level up your Materia and get the complete Master set.
The card game in Final Fantasy VIII. Many players clocked more time playing Triple Triad than playing the rest of the game put together, possibly because FF8's Junctioning system made Triple Triad the local flavor of Level Grinding. It's lampshaded on at least one occasion; start a card game with Ellone on the Lunar Station, with all hell about to break loose thanks to the Lunar Cry, and she'll reply incredulously, "You wanna play cards now?!"
The Spoony One: "EVERYONE, FALL BACK! THEY'RE COMING AT US FROM ALL SIDES! WE NEED A BARRIER BETWEEN US AND THE SNAKES what, cards? Yeah, I got a minute."
To clarify the FF8 example above: Pretty much every enemy you ever fight in that game is scaled to your level, and it's completely possible (especially if you try traditional level grinding) to find yourself unable to progress because the scaling assumes that you're going to be upgrading equipment, spells, GFs, and such as you level. Playing the card game allowed you to win cards, which you could turn into items, which could then be turned into spells to link you your stats to increase your power. Probably the only game where playing a card game is the Disc One Nuke.
Sphere Break, on the other hand, was only fun for people who enjoy math. You'll play it to get the Lady Luck Dressphere and then curse those wasted hours for the rest of your life.
But if you DO enjoy math - best minigame ever. Too bad there's hardly any rewards outside of more coins...to play Sphere Break with.
Blitzball in FFX-2 may have been even more addictive than it was before, despite no longer being able to directly control the players.
Gunner's Gauntlet is fun, until you realize there's a temple version that plays like a first-person shooter. There goes the rest of your month.
Final Fantasy XII and Final Fantasy Tactics A2 are so full of sidequests that some players actually forget what the main storyline is. Though in most cases a game with excessive sidequests isn't considered a bad thing, Final Fantasy XII diverges from the rest of the series by making said sidequests have absolutely nothing to do with the actual plot or characters of the game.
Subverted in Final Fantasy XIII. In Chapter 8, two of your party members visit Nautilus Park, but before the game gives you a chance to really start doing anything, you get captured by soldiers and the rest of the party has to rescue them.
Arguably played straight with the missions that become available in Chapter 11. Completing them all can take more time than some players are willing to spend. Not only that, but in order to get all the Trophies/Achievements, you not only have to complete them all, you have to five star them all.
Final Fantasy XIII-2 has the Serendipity timeline. The game teases you with it early on and lets you in toward the middle. The Chocobo races are just as time-consuming as they were in VII. There are also slot machines and cards which become available through DLC. That's right. Not only do they want your gil, they want your real money now too. As if to lampshade this trope, it's stated that Serendipity exists outside of time.
In general, any game whatsoever that features a ridiculously fun multiplayer mode will inevitably be a huge source of this, especially if all the features in the multiplayer are just as vast as in the single-player story. Let alone how much more fun it is to play a game with your friends anyway.
For example, Perfect Dark's Combat Simulator. Seeing as it's the only mode available to even play if you don't have an Expansion Pak, they had to make it really addictive. And quite so: there are more levels and maps than in single-player, you can set every weapon that appears, fight with up to 12 opponents, select the behaviors of the AI, customize damage/health settings, choose from several different game modes, switch from free-for-alls to team battles... as at least one reviewer has noted, it's amazing that the old N64 cartridge didn't explode from everything the multiplayer has to offer alone.
Things about GTA4 will find on YouTube: Horrific one-car accidents, horrific two-car accidents, horrific multiple-car accidents, horrific motorcycle accidents, horrific helicopter accidents, vehicular homicide, insane successful stunt jumps, insane unsuccessful stunt jumps, helicopters plummeting out of the sky for various reasons, falls off of buildings, falls out of helicopters, falls from the edge of space, slamming into buildings at high speed, shoving people down stairs, off of cliffs, and into traffic, cops doing ridiculous dance routines, shooting each other, and jumping to their deaths, outrageous ragdoll physics, frictionless/zero gravity chaos, massive tidal waves, and people and cars being launched skyward by playground equipment. Things you will not find: "Missions", "side missions", "bowling", "talking", or whatever the heck it is you're supposed to do in GTA4.
Grand Theft Auto V ups the anti in almost every way in this. Getting sidetracked might not even be getting sidetracked in this game. The entire game seems to be made up of getting sidetracked. Now if you'll excuse me, I have a tee off to get to. In game.
Saints Row took this trope and made a game around it. It's supposed to be a GTA clone. In reality doing missions is just another minigame, along with customizing cars, buying bling for your avatar, spraying the streets with the contents of a septic truck against the clock, car surfing, flying under every bridge in town, landing on rooftops, then basejumping off and landing in the back seat of a gang vehicle (all of these unlock rewards), shooting other gangs from the window of said gang vehicle for a reward, putting out fires, towing hot cars, playing a pimp (or ho), driving a celebrity's Bentley and running news vans off the road, taxi driving, jumping in the path of incoming cars for money, tagging, robbing stores, blowing up as much stuff as possible with an infinite ammo rocket launcher, throwing crazed fans into jet engines, engaging in fisticuffs, demolition derby, demolition derby with harvesting combines, street racing, jetski racing, doing stunt jumps, assassinating people and getting drunk or stoned... And streaking.
Iji gets extra points for doing this in universe with the Easter Egg Minigame Hero 3D. It's a very addicting action game in it's own right, but upon reviewing some logbooks it is stated that one of the aliens programmed it in his spare time, and left it there in hopes that the "Human Anomaly" will be distracted enough by it that they can just walk up and capture her.
And pretty much every Bomberman game that includes the classic battle mode, which is nearly every Bomberman games. They've added all kinds of new stuff over the years, but most people play just for that mode.
The Fishing Hole in The Legend of Zelda: Ocarina of Time is well-known for its addictive properties. Even after winning the available prizes, you can waste ages in there, looking for the elusive Hylian Loach. It was the result of one of the game designers goofing off while working on the Water Temple; he'd isolated a room with a water pool and some fish for his own amusement, and, when found out, the rest of the team liked the idea enough to throw it in.
Ocarina of Time also featured the Horseback Archery course in the Gerudo Fortress. Ganon can wait. Link NEEDS his perfect score!
Parodied here, where Link is too busy either fishing or chasing chickens to do anything that actually involves saving Hyrule.
Someone, with help from others, made sheet music for Ocarina of Time, since the Ocarina is a full-featured instrument, not a prefabricated spellbook.
The Fishing Hole returned in Twilight Princess. Still awesome, and this time using the Wii controls.
Be honest, in The Wind Waker you spent four hours sailing around, exploring unimportant islands, looking for treasure, and filling in your map as soon as you were allowed to sail around freely.
Averted in Baten Kaitos Origins. You'd be spending all your time at the coliseum if it weren't for the fact that you can only fight a few matches per class. Once you clear the class, you have to wait for the story to progress before you are notified you can continue fighting new coliseum matches.
If you are intent on winning all of the swoop races in Knights of the Old Republic, you will probably spend enough effort on them that you end up at a loss with the track fees, unless Save Scumming is used to cheat them. It doesn't help that getting the best time is literally a difference counted in fractions of a second. The second game is slightly more forgiving on this account.
"Beating" everyone at the cardgame Pazaak takes even longer. Most Pazaak players will only play for a certain amount of time (generally until you've beaten them a certain number times in a row), after which they won't play for money any more. Even with Save Scumming, each game can take a few minutes to play, and if you're trying to win five straight games or so with a dozen different people... well... you do the math!
In Star Wars: The Old Republic, codex hunting and datacron puzzles can kill days worth of play. There are also Heroic-level sidequests that reset daily, PvP, the space battle rail-shooter, flashpoints, bonus series for each planet after you've completed the main class quests. Not to mention XP just for filling out the map. It's not unheard of for players to hit the level cap around Alderaan (meant for levels 28-35, with a Nintendo Hard bonus series going to Level 43).
The Tower of Tragedy quiz and "shootout" modes in Banjo-Tooie were so neat, Rare included them as their own mini-games. They're also ridiculously addictive, and make great multiplayer fodder.
One can spend more concentrated time building vehicles in Banjo-Kazooie: Nuts and Bolts than actually focusing on Jiggy Challenges.
Tekken Tag Tournament's Tekken Bowl mode is highly addictive. It is likely if you're with friends you will play this more than actual fights.
It's been around since Dragon Quest II. The NES edition included a simple "lottery" (more like a slot machine). Even if the player ran out of tickets, there was always the option to reset and try again.
Test Drive Unlimited 2 features a casino that is unlocked for 800 Atari Tokens (Which is $10.00 in real money), what makes it worth playing is the ability win both an Audi R8 Spyder and a Spyker C8 Aileron Spyder if you're willing to spend the time and (sometimes) money to get the one-million tokens for just the R8. (The conversion rate for Casino Tokens is 1 Token = 2$, requiring a whopping 2 million dollars to buy the tokens for it).
And as for Pokémon, in the first generation games winning a large sum of coins at the casino was the only way to get Porygon, outside of spending an even larger sum of money.
However, you can get Dratini which evolves into Dragonair, then Dragonite. You can also get Pokémon you have normally would have trouble catching, such as Abra (Teleportation from battle) and Clefairy (Hard to find in Mt. Moon), and Scyther (Safari Zone).
Likewise, in later titles the Casino Gift Shop gives out the most useful TMs and items, so the gambling really does pay off, especially for "Stop Having Fun" Guys.
New to the scene in HeartGold and SoulSilver is the "Voltorb Flip" game. Your total coins can only go up, because you're not actually betting in this game. On the other hand, they compensate for this by making it take even longer to make just as much money as you could by Save Scumming the slots... which just results in even more incentive to play it for hours.
Or you can import your Technical Machines and whatever else you would like, by placing them on your Ruby/Sapphire/EmeraldPokémon as held items and importing them through Pal Park.
Ruby, Sapphire, Emerald, Diamond, Pearl, and Platinum have Pokémon Contests, which involve a different set of stats entirely, and are rightly a whole other game. Imagine a competitive beauty pageant, for Pokémon. HeartGold and SoulSilver instead has the Pokéathlon, which is track and field events for Pokémon.
Averted in Pokémon Black and White and later. Due to EU anti-gambling laws, there aren't going to be any more Game Corners in the series, period. However, you do get to have your Mons perform in a musical.
Back with a vengeance in Pokémon Black 2 and White 2 in the form of Pokéstar Studios. Shooting movies there is very addictive, and you'll be staying in Virbank City long after beating Roxie because of how fun it is to do so.
For those who love battling, the Battle Subway and Pokémon World Tournament are the places in Unova to go! The former is a seven-battle system that pits you up against a wide variety of Pokémon. Although the regular lines can be pretty easy up until the last eight battles or so, the Super lines are perfect for competitive-level trainers who need something to try out their tactics on. Endless, unpredictable battling means nothing is the same, and even other trainers or an in-game one can join, too! The latter is a tournament-style system that pits you against almost every Gym Leader and Champion in the series. It's useful considering that you earn points needed to buy valuable held items and TMs by doing so. Battle-loving trainers will have a blast.
In Pokémon Mystery Dungeon: Gates to Infinity, with the addition of facility building, similar to Join Avenue above, you can get distracted from the main plot by focusing on grinding materials and improving your Paradise. Not to mention the minigames added like Sunken Treasure and Prize Palace.
Pokémon X and Y has two types of minigames that can be accessed anywhere: Pokemon-Amie and Super Training.
Pokemon-Amie is a way to build relationships with your Pokemon. You can pet them, feed them desserts, and play smaller games that make your Pokemon friendlier toward you. This causes your Pokémon to gain many benefits during battles, such as being more likely to land critical hits, recovering from major status conditions, and surviving attacks that would have otherwise KO'd them. Thus, it's very easy to get stuck on this mode if you have a lot of free time.
Super Training is a set of minigames where your Pokemon kicks soccer balls into a balloon to try and pop it as fast as possible. This has the gameplay purpose of increasing your Pokemon's Effort Values which can be manipulated for Min-Maxing, and is much, much easier than the previous way of killing a certain type of Pokemon over and over again. Of course, it still takes a long time to complete, so players find themselves spending a lot of time in the minigames, causing this trope.
Sonic the Hedgehog 2 has Casino Night, which can cause some players to lose by running out of time. Yes, the slot machines are that addictive!
In that vein, most of the "theme park" Zones in the entirety of the series invoke this both in-game and during play; all of them...except for Sonic 3's infamous Carnival Night...
Don't forget the Special Zones where you tried to get the Chaos Emeralds. Those were a game in their own right.
Chao Raising in the Sonic Adventure games. For some people, it's the only reason why they still play those games.
In the first world, "Clowny Island," there's a mini-game that lets you build custom roller coasters for the titular robot to ride in. While there is a goal to it (the coaster's path must hit certain targets), more than one reviewer has noted its extreme distraction potential. "Just one more coaster, I swear!"
The second world, "Paint Misbehavin'", features a paintball-spewing vehicle called the HoverSplat. The paintballs are there so you can solve color-based puzzles... but the fun of them is using them to paint the entire level crazy colors.
The fifth world, "Pyramid Scheme," features, in its Lethal Lava Land half, the "Glider Bike"—A motorcycle with BAT WINGS that FLIES. If you think you can resist the allure of flying around inside a volcano while doing aerial tricks on a motorcycle, you are very, very wrong.
Dead Space has a mini-game known as "Zero-G Basketball" or "Z-Ball." Even though Isaac is playing by himself, it's still a lot of fun.
Road Rash 64. One of the unlockable benefits is Insanity Bikes (AKA jumps really far). One of the levels is an airport runway with a little jump at the end. Even if you blow the jump, you still go hurtling hella far. So very, addictive.
A lot of the games were featured in the earlier Super Mario 64 DS remake. Whichever card in your DS, the Bob-omb Sorting minigame is enough to forget that you've actually got a proper game to play through.
Kaos mode in State of Emergency strips out the storyline and just lets you wreak havoc. It's actually more fun than the story mode.
Nippon Ichi strategy games tend to fall into this trope due to the massive amounts of Level Grinding it takes to tackle the Bonus Boss battle(s); one cycle of the game is completable in twenty to thirty hours, but many more are required to acquire and power up that Infinity+1 Sword.
Not to mention the Dark Assembly in the various games. There are two ways to handle it. One is to basically force every bill you could ever want through - this turns the area into yet another place to go level grind (with getting some sort of improvement in addition to levels). The other is an in-game version of Bribing Your Way to Victory, in which you use the spoils you're not using from other level-grinding trips as bribes to get everything past without fighting. Each version is self-perpetuating, as well - the senators remember what happened to them in previous votes, so they'll be more prone to blocking your bills if fought before (necessitating another fight) and more prone to passing your bills if sufficiently bribed in the past (giving you the chance to bribe other senators).
The Fallout series is especially guilty of this, where many of the sidequests or just exploring the maps draws you away from the main story, to the point where the first two games put a time limit on the first major quest to keep you focused.
The third game has no such time limit until the final part of the main quest. It is very easy to get caught up in exploring and doing sidequests right from the moment you leave the vault, to the point which the player can hit the level cap before really beginning the main quest.
Since Fallout 3 doesn't let you keep exploring after completing the rather short main quest, it's more preferable to tackle as many sidequests as possible first and level up.
At least the Broken SteelDLC raises the level cap from 20 to 30 immediately when installed, so you don't have to worry about hitting 20 and having to finish the main quest in order to start Broken Steel and progress on to 30.
And in Fallout: New Vegas, if you like gambling, on a new game you can start walking towards the Strip (mountaineering pastthe Cazadores and Deathclaws), easily collect 2000 caps on the way for the entry check, and spend the rest of the game gambling at slots, roulette, or blackjack, sleeping in the casinos and buying marked up food from casino bars, until you run out of money. Just like real life Vegas.
Characters with Luck of at least 7 will probably run into the jackpot limits and get barred from gambling in about an hour of gameplay or two. The devs put this in to keep the players from breaking the in-game economy, but it also has the effect of blunting this trope.
The Elder Scrolls IV: Oblivion takes this trope to such an extreme that, after you get a feel for it, the main quest seems like the most marginal sidequest. Sometimes you get so engrossed in wandering Cyrodiil that the Oblivion Gates everywhere are more an annoyance than your reason for adventuring.
The Oblivion Gates themselves can be diversion for those rune-hunting, gathering daedric herbs, or going for 100% Completion. That's why you do all of that, open the Gates, and do it again with more monsters.
Skyrim has loads of dragons even before you get the main quest really rolling, and they're a real nuisance if you didn't get good at killing things or surviving attacks and are just trying to catch butterflies for your potion shop or explore to get 100% Completion. You can own shops, become nobility, rise to be the head of every guild, hunt random-encounter dragons and find every Wall to add to your Shouts, etc., and all that's unmodded.
Morrowind fits the bill too. Apparently, many players got lost and just wandered around in their few first games. When you finally decide to start a game in which you'll stick to the main quest, you realise how much more fun it was to simply wander around.
In fact, Morrowind is such a good example of this trope that there's a popular mod which removes the main quest from the game.
Skyrim has one too, and not just one; a combination of mods can disable the main quest, remove your ability to shout, and dump you anywhere in Skyrim, effectively erasing any and all ties you had to the original main quest (and the theme of the game).
Every Elder Scrolls game can be considered an example of this; in fact, it's been one of the driving designs of the games since day one.
In-game books also have a tendency to do this, as the writing of the books is at least as good as the writing of the game.
Xenosaga Episode I's card minigame is incredibly addictive.
The poker minigame is not only addictive, it's the best way to make money, if you know what you're doing.
Xenosaga Episode III has Hakox, which could have been released by itself as a sweet budget title.
Xenoblade, hoo boy. This game may well hold the record for just how early it's possible to get sidetracked: the first town alone contains literally dozens of sidequests, as well as around 50 unique, named NPCs to register in a chart detailing their relationships with all other NPCs! A player could spend hours doing sidequests before even leaving the first town! By the time one is done with sidequests and moves on with the main story (if only for having no more quests to do), the party can easily be many hours and about a dozen levels past what the game expects.
In Super Mario RPG, after a certain point you can go back to the first town and buy a Gameboy game from a kid who had been playing it the whole game(he sells it to you because he finally beat it). It's an insanely addictive Space Invaders clone where you can create giant combos for MASSIVE POINTS.
There's also Grate Guy's Casino (assuming you can figure out how to get to it without a guide anyway). Offers two rather terrible games with high chances of losing, but also a game from Grate Guy himself (essentially a coin flip game) with a prize if you beat him 100 times. Said item is a moderately powerful, infinite-use attack item, so it's well worth the considerable amount of time it takes to get.
Might and Magic VII featured Arcomage, a card game that can be played at any tavern. Additionally, every tavern had different house rules.
The NES games from the first Animal Crossing. This very trope was the reason they never made a return in future games.
Super Paper Mario has the arcade. Four insanely addictive and incredibly fun minigames. Many players would only leave to spend their tokens on that which they could sell, do so, then return with more money. Even if they eventually got bored of the game they were playing, there were still three more.
If you got bored of Tilt Island, there is no helping you.
Kingdom Hearts: Birth by Sleep has more distracting and addictive minigames than you can shake a stick at. Command Board can suck away hours of playtime each time the player unlocks a new game board. And then there's Disney Town, which is basically the Gold Saucer of Kingdom Hearts— full of incredibly fun and addicting minigames. And that's not even including the multiplayer aspect in the Mirage Arena, which lets the player do all of this and more with friends... suffice it to say, it's very, very easy to completely disregard the story.
It doesn't help that they give you very good incentive: the top two rounds (in the original) give out the Infinity +1 Key and the most powerful Shotlocks in the game - including Lingering Will's Ultima Cannon! That in itself wouldn't be too bad... unless you're a Billy-no-blokes, because the Mirage Arena is designed for multiplayer. The Shotlocks are guarded by the third and fourth forms of the evolving SNK Boss.
To say nothing of the command menu and melding process, for some gamers, who will spend HOURS tweaking and mastering their commands, because... Gotta Meld 'Em All.
Kingdom Hearts 3D [Dream Drop Distance] has Spirits (friendly Dream Eaters) helping you in battle. The game includes a fully functional virtual pet simulator for taking care of them - one can easily get distracted from the main point of the game thanks to this, though your Spirits do gain some battle prowess along the way.
Absolutely ANY games with Level Editors and/or create a character modes. Seriously, any sandbox type game with these features (any theme park or rollercoaster game, Spore), will have probably more people using the features than the single player mode, and for Super Smash Bros. Brawl alone there are a heck of a lot of people spending more time on the Stage Builder than the main game itself.
Sauerbraten. It's a free FPS game with in-game ONLINE CO-OP LEVEL EDITING.
Already no stranger to create-a-whatsit modes, the WWE wrestling game series has recently added in a create-a-story mode. For anyone who's ever said they could pull better plot twists out of their ass than Vince Russo could actually sit down and write, it's both a dream come true and the sputtering death of whatever social life they had.
The other edit modes are no slouch either, with the ability to create wrestlers, move sets, arenas, logos, et al becoming so vast 2K Games have to regularly cull those with low votes/downloads before their servers blow up. A casual search for John Cena alone would reveal upwards of fifty pages of him, and if you can name a wrestler, character or real celebrity odds are there' not just one version of them but several.
TimeSplitters, arguably more time was spent making levels than actually seeing any action. Though the challenges are also fun in and of itself. Then again, this may have been the game itself since the first installment was a fairly bland "Get MacGuffin and return to the starting point"
Legend Of The Mystical Ninja features an entire level called "Amusement Park," which consists almost entirely of mini-games such as concentration, horse racing, a paint contest, and a quiz gameshow with a ridiculously huge cash prize. Players can and do waste hours here.
Not to mention that it has one of the shops where you can buy the Hourglass item, adding time to the ever-ticking time limit at the top of the screen. You can't just waste hours here, you can buy them and waste more!
Doing these is actually useful as money helps a ton when buying food, armor, shoes, or extra lives later on in the game. Something that's really useless, though, are the arcade games like Gradius and Arkanoid, except for fun.
Which was apparently later ripped off into a standalone program for easier editing. Also, the standalone program allows for sharps and flats. The original could only compose in C major. Or possibly A minor, but...
It's likely that some people who bought Ape Escape 3 bought it for the Metal Gear Solid parody minigame, and then found themselves enjoying the cute monkey game that came free with it.
Similarly, there are many of us who have popped the disc for Metal Gear Solid 3 and ended up catching monkeys for hours on end.
Ape Escape 2 has the soccer minigame which could well be its own game trying to win against the other team.
Star Ocean Till The End Of Time actually has an item that will have you ignoring the battles because it's just so much fun to roll around. It's also easy to get caught up for weeks playing games in Gemity, although that's partly because the Bunny Racing game is so luck-dependent it will take you weeks to win all the prizes.
Star Ocean: The Second Story also had the bunny-racing game, which was just as hard (if not harder) to win at. At the very least, there's only one prize there that you can't get elsewhere, but seeing as it's possibly the best set of footwear outside of the game's Bonus Dungeon...
Not to mention in both Star Ocean 2 and 3 you can go back and visit places that you can't return to normally, either because the planet no longer exists, or the location is on a different planet. Now add on that in every city you can disband your team and interact to get special endings. SO2 had 81 possible endings, only available through team-city interactions.
Star Ocean The Last Hope brings back the Bunny Racing minigame as well, though this time around there is a small degree of control of the bunnies while they race, and you can affect various stats like speed, endurance, and such based on foods you feed it. Having a small degree of control over the outcome makes it quite fun to play.
Plants vs. Zombies has an incredible amount of features beyond the standard Adventure mode. And as the in-game prices of new items for use in Adventure mode skyrocket, you may find yourself turning to these alternate features to build up your cash supply before braving the next level.
This is more of a subjective one, but just about every Unreal Tournament game except UT3 had amazing mods and "mutators" (miniature mods that could be switched on and off in-game).
Lufia II: Rise of the Sinistrals's Ancient Cave is this. A 100-level randomly-generated dungeon where equipment and spells are randomly distributed, with ever-increasingly powerful monsters and a giant boss at the end. It even has collectible Iris Treasures which serve no purpose. The worst part is the developers knew it: After beating the New Game+ mode, you're given the Gift Mode, which strands you in the town next to the Ancient Cave with the ability to select which members join your party from every playable character in the game. It was so popular that it spawned a phone release with JUST the Ancient Cave and nothing else.
And don't forget Forfeit Island, which holds the traditional casino. And a pawn shop, where you can buy back the stuff you sold. Or fed to your Capsule Monster to make it grow into a stronger form. Hmm...
The Millenium Puzzle/Puzzle Box in the Wild AR Ms series. Many tales are heard of gamers stopping in the thick of the plot upon opening up new sections of the map just to seek and solve every Puzzle Box they can at that point.
Call of Duty: World at War had the Nazi Zombies unlockable survival mini game. Given this has online leaderboards and co-op multiplayer, one can literally spend hours playing sometimes instead of the normal modes. Then it got people making their own maps for the PC version... then it got three downloadable bonus maps to buy (or get for free for the PC version), complete with traps such as electro-shock fences and swinging maces, and various power ups...
And then they released Call of Duty for iPhone. Which game? Modern Warfare? No. Nazi Zombies. Many people played the campaign once or twice, online a handful of times, and Nazi Zombies for hours.
Call of Duty: Black Ops outdoes itself by giving us several further Nazi Zombies maps. The default one lets you play as Fidel Castro and JFK, then among the DLC maps there was Call of the Dead. What's Call of the Dead? This is Call of the Dead.
EA Sports' NBA Live series, starting in 2005, includes the All-Star Weekend dunk contest as a mini-game. Doing 720 degree dunks is way more exciting than grinding out a full season.
While still a core aspect of the main game, some people spend ridiculous amounts of time tweaking and customizing their mechs in Armored Core.
Fable had "Card Pairs" in Bowerstone South. Pretty fun and fairly easy to master, with the added bonus of earning you all the cash you would ever need within a few hours.
The minigames at the festival in Wild AR Ms take up way too much time. It's perhaps fortunate that you can only play them while the festival is going on.
Dark Cloud 2 gave you an option to take pictures of items and mix them to create possible new weapons. Cue every time you get to any new place, you whip out the camera and compulsively take pictures of everything and mixing them to get something new. Another 'feature' of this game and it's prequel was placing cities so everyone's 100% happy, frequently meaning you have to rearrange an entire town repeatedly.
Fortunately, in Dark Cloud 2 it is possible to build more houses in an area even after achieving 100% completion, so those who enjoy that aspect of the game can continue playing around with it after they finish the area.
Both games also feature a Fishing Minigame. It was surprisingly deep in 2 - giving you two types of fishing poles that are used quite differently, the ability to level up your fishing poles extensively, a contest that rewards you for catching the largest fish, and the ability to put fish in an aquarium to prepare them for a fish race!
There is also a golf minigame called Spheda which gives surprisingly good rewards on certain floors. After beating the game, you unlock the ability to play through a special Spheda course. The only reward for beating it is to see how low you can get your score!
Finally, every floor in the game offers 3 or 4 medals by completing certain criteria. Getting all these medals requires doing a good bit of the aforementioned fishing and Spheda.
City of Heroes has the invention system and in-game market. Instead of, oh, saving (or terrorizing) the City, some players log in just craft and sell in-game items. For in-game money. Just to buy more expensive things to sell for higher prices to get MORE in-game money. All while paying REAL money every month to do this.
The Winter-themed chalet with slopes and a bobsled run also constitute this.
Base construction. Originally intended as a PVP mini-game cross between Space Management and Tower Defense (like Dungeon Keeper without the minions), but the PVP raid feature never worked properly and was scrapped, leaving bases only useful for item storage and shortcutting between zones. Nonetheless, some supergroups built huge and elaborate bases just to have a pretty place to hang out when not on missions... and spent over a hundred hours perfecting it.
Similar to the City of Heroes example above, in World of Warcraft, players will often spend just as much time leveling their professions as they will actually leveling normally. It becomes really bad when one reaches the current end level content of the game, where gathering the materials and recipes necessary to improve your professions is actually tied directly to the high level daily quests and dungeons, making it almost a subversion of this trope. However, there are plenty of people who prefer simply loitering about the local auction house and simply buying whatever they need from the more active players, just so they can hang out in the Trade chat channel and barter their wares...you know, rather than actually play the game they spend real money on each month. On the other hand, players will also specifically create characters that just go out and gather materials so they can sell them to the higher level characters looking to improve their professions. This method is even recommended to beginning players, both so they can level faster without having to go out of their way to level their professions (purposefully subverting this trope) and so they can get a bit of extra money during their low level grind.
The darts minigame in Backyard Baseball 2005 is regarded as much more entertaining than the main game (which, like all sports games, gets boring after a while).
In No More Heroes, the side-jobs were largely regarded as a minor obstacle to blaze through in order to unlock more lucrative assassination jobs. So what happens in No More Heroes 2: Desperate Struggle? They get turned into faux 8-bit minigames... and they're just as fun as the main game itself. In particular, "Bug Out" and "Tile in Style" are easily liable to suck your time away. Oh, and if you're not into those, there's the faux-MoeShoot 'em Up in Travis' room, which allows you to blast the ages away...
The eventual discovery of a hidden "Special" mode in the latter, unlocked by beating the game on Hard without dying once, did not help.
Project Gotham Racing 2 featured a rather innocuous looking arcade-game box in each of your in-game garages. What should that box guard but the treasure that is Geometry Wars. Successful enough in it's own right to sell well on Xbox Live Arcade, as well as spinning off a sequel and a WiiWare adaptation.
Can happen in Patapon, but fortunately the materials you gain from doing so are necessary for army-building.
After beating the first playthrough of A Witch's Tale, you get to play a game of Black Jack against all the other characters.
Kirby 64 contains, for no adequately explained reason, three mini-games in addition to the main game. That doesn't stop them from being a total time-suck, and great fun if you happen to play them with your friends.
It helps that the 100-Yard Hop minigame has the Gorumet Race theme from Kirby Super Star as its BGM.
Spyro 3. Skateboarding minigame. You know what I'm talking about.
The Keterburg casino in Tales of the Abyss is the only way to get the Joke Weapons. Since the weapon graphics in cutscenes do change to reflect the weapons the characters equipped, wasting time at the casino to get the joke weapons can easily be worth it for the opportunity to watch Jade wave a giant finger pointer around in the midst of a serious scene.
Abyss has a really weird minigame in Nam Cobanda Isle, where you hit a bunch of spots with Meiu (panels on the floor, moving panels... that stuff), and you get points every time you do it, especially if you hit the panel that puts up the flags. It's terribly distracting, because if you leave the area, you have to start getting the 99999 points all over again, and you don't even get that great of a prize, other than saying you spent hours doing nothing. Also in Nam Cobanda Isle, you have Dragon Buster, and from it you can get TWO titles for Luke. THEN in Ketterburg, you have the casino, where you can choose to play Poker or Nephry Ball (which is essentially the lotto). With this, you get chips and can buy very unique items, almost all of which can only be found at the Casino.
Tales of Vesperia has a Nam Cobanda Isle itself and the opportunity to play the ever-so-addicting casino games. There's also a minigame in another area where you have to accurately predict if the next number is higher or lower than the one preceding it.
Also, the working Casino in Tales of Symphonia for the Playstation 2. None of the prices were so great - except the pretty cheap Devils Arms weapon. Or Raine's bunny outfit, costing the most chips.
Most recent Nancy Drew PC games will have some type of arcade game in them and some hard to obtain prize and/or Easter egg (literally). Many players will get sidetracked halfway through the mystery because they want the prize, and then proceed to spend more time going after it than on the rest of the game overall. The box that's for sale for $99.90 and the rather addictive Land Rush minigame in Trail of the Twister stick out as the epitome of this trope, espically as it takes 50 to 75 plays on the arcade game to get the box.
The Coin Shooter minigame in Super Smash Bros. Brawl. There are other ways of getting trophies and stickers, but you'll keep your finger hovering over the Fire button for hours just waiting for a new/rare one to float into the playing field.
Way back in Super Mario Bros. 3 for the NES, if you played it two player, there was a version of the original Mario Bros. game (and, if you played enough times to get through the very long repeating rotation of modes, a couple of other two-player minigames). You selected it by going to your 'opponent'/co-player on the map, and clicking, or by clicking as they tried to run past you! Whoever won the minigame got to have the next turn, and the players moved so that the winner got the location where the battle was fought. So (depending on where the players were on the map) you could be trapped in an endless cycle of battling to play the next level. Not to mention you could steal the emblems you win at the end of levels so you could also start a cycle to get those back.
Fire Emblem: The Sacred Stones had the Tower of Valni, the Lagdou Ruins, and random battles on the world map. In order to unlock them, one did have to play part of the way into the main game, but after that you could go through them as many times as you wanted. It helps that the ruins and tower both had rare treasure in them and that certain random battles could be used to steal items from enemies with a glitch.
The main menu of Sumotori can keep you entertained for hours. It might even be more time than you will spend actually playing the main game, because each round lasts only a few seconds. However, after each round, the opponents try to bow, and THAT is when the fun starts. And then there's the secret mode...
And then the sequel, Sumotori Dreams, added 4 player mode and more maps. And you can't control all 4 characters. Which means lots of people will simply watch the computer battle for four seconds, and fall repeatedly for four minutes. Over and over again. If you choose to actually play for those four seconds, then you can control your character even after the round ends. These two games are made from 5% very fun game and 95% very fun other things.
Breath of Fire: Dragon Quarter has an Ant colony you can raise, working in many of the same ways that the fairies do in III. A much needed addition to a game where quite literally every step you walk is one step closer to your death. This makes returning to towns to restock on healing supplies and buying new armor and weapons that you couldn't afford the first time you got to the town quite risky to finishing the entire game.
The Saboteur: The game's option of going around the city and countryside to destroy the various Nazi war and occupation equipment is probably what gave this game it's name, more than the actual French Resistance aspect. You'll spend a lot of time blowing up bridges, searchlights, AA guns, sniper nests, occupation towers, artillery, propaganda speakers, fuel depots, and various other things.
The Oregon Trail spinoff Yukon Trail had a card game you could play and gamble on. It's far too addictive.
Every year, Kingdom of Loathing celebrates Crimbo with at least two weeks worth of dedicated content, during which most players' ascensions fall to the wayside. Other random events that eventually become Lost Forever also become the distracting shiny, such as "Biggs' Digs" and the subsequent skeletal apocalypse in 2010.
Although you do have to pay attention to the main storyline of the Mass Effect games eventually, you can waste an awful lot of time exploring/scanning what seems like every single planet in the known galaxy, if you'd like. This can lead to some rather funny Mood Dissonance, as you immediately go from angrily telling someone you have to hurry, you have to save the galaxy... and then immediately hopping back in your spaceship to probe another couple dozen planets, and maybe leisurely explore an abandoned space station or two.
The Citadel DLC includes, among other things... decorating your apartment and gambling at a casino. And it's during the middle of the apocalyptic Reaper invasion.
Oh, it's got that and more, including a combat simulator arena, a video arcade (with a claw machine), and throwing a rager for your friends. In a brightly lit neon futuristic wonderland.
There are many, many parodies of the fact that you're spending an often-significant amount of time romancing your crew members as the galaxy races towards oblivion. For three games.
Although there isn't much to do in Shadow of the Colossus other than killing the colossi and sightseeing, you'll find yourself captivated enough by the scenery to sink hours into just wandering around the place and drinking in the beauty of the setting. Scenery Porn at its finest.
Justified though, there are certain lizards you must kill to increase your grip power and fruit to raise your HP. But you probably wouldn't know that.
There are also the Time attacks after killing the Colossi which can net you features; The Parachute, Explosive Arrows, but the best is a Sword that can kill a colossus in 2-3 hits. So if you wanted this stuff or wanted to experience a certain battle again because it was "epic" to you, then go nuts.
The Yakuza series is most likely the king of this trope. There are dozens of different minigames to play through, each wildly different. Batting cages, casino games, Japanese casino games (like cee-lo), mahjong, arcade games, even crane games where can win little stuffed toys. There's also an entire golfing game to play through, karaoke songs to sing, diners to visit for completion purposes, hostess parlors to visit (and ladies to woo), and more. Then there's also the arena to fight in. It's far too easy to simply sink in days and days and days worth of gaming time just getting sidetracked as you, a complete and utter badass Yakuza boss, play golf or try to win stuffed animals.
Because actually winning a game of Nethack is a nigh-impossible task (at least until several months or years of gameplay, even if you do use the Internet to look up spoilers), most casual players don't pay much attention to the main quest, possibly not even remembering what it is.
While there is technically no way to actually 'beat' Dwarf Fortress, and most of the game is doing whatever you think is fun, there are some things people do that go above and beyond simple 'Because I felt like it'. These are called Mega Projects. They can range from closing the Fortress off from the outside world and flooding the mapnote with either water or magma; whatever tickles your fancy, to creating a massive stone ceiling blocking out all that pesky sunlight, to constructing statues of Dwarves (and, in one extremely surreal case, the Elven Kingof the Dwarves) that are hundreds of feet tall, made of pure gold, and with magma for eyes).
The sheer number of quests, sidegames accessed by quests and achievements found in World of Warcraft can easily make you forget about that Arthas guy with the cool sword, or that dragon that wrecked Stormwind
With the thousands of characters potentially available to use, M.U.G.E.N already makes for a big enough time-sink. Add in the nigh-limitless customization options you have via stages, soundtracks and graphics, and you can kiss your free time goodbye. And that's without even getting into the fact that with a little coding know-how and a lot of patience, you can create your own new content from scratch.
Persona 1 and Persona 2 both have casinos that feature slots, video poker, blackjack, and (in P2 only) bingo. Playing nets you coin tokens that you can exchange for weapons, armor, spell cards, and other useful stuff. Unless you're on an emulator abusing save states, however, be prepared to spend hours on these games to get the shiny stuff. In P2, Yukino even laments all the time one of her old friends (you, the player character in P1) spent in the casino in the midst of a crisis.
Descent 3 introduces speed tunnels to the series, which catapult the player from one end to the other at high speed. And they are hella fun to ride! Which is why one of the secret levels is made of nothing but speed tunnels that stretch for miles. You will spend more time screwing around in this one level than you will the entire campaign.
The hacking minigame in Deus Ex: Human Revolution is going to eat up so much of your time just for the rewards, experience, and exploration it offers. Several important mission segments of the game feature large rooms with up to a dozen computer and security terminals, and you're going to have a hard time resisting the tempation to just stop and spend twenty minutes scouring the room for things to hack.
Crackdown is nominally about fighting gang leaders (or mutants, in the sequel), but you're going to spend a lot of time leaping from building to building and hunting down orbs. And having a lot of fun doing it.
In The Sims, especially 2 and 3, and especially if you download custom content, creating Sims and building and designing houses are often so fun people make Sims and houses they never actually play with. Some people end up creating beautifully decorated Sim houses which look almost like real people's houses, but unfortunately are totally uninhabitable by Sims. Downloading custom content on its own can have this effect too.
Megaplex Madness, Megaplex Madness: Summer Blockbuster and Busy Bea's Halftime Hustle all feature an arcade with extremely addictive unlockable minigames with cash rewards for every so many levels or points, making it all too easy to start playing in hopes of winning enough for a coveted theater/stadium upgrade and then stay until you've run out of tokens.
It's easy to get sidetracked by the Golden Egg in Angry Birds, to get so busy trying to hit said Golden Egg that you wait and do the actual level after you get the Egg.
Tobal No 1 was a unique take on fighting games set in 3D back in the early days of the genre. While it was unique enough on it's own to be fun, it also included a rather hard dungeon exploration mode with randomly generated dungeons, monsters to fight that would test your skills (and were not just reskins of the fighters available) and was genuinely fun. After the fighting was done, you could count on hours and hours of replay in the dungeon.
Soul Calibur III included a mode that allowed you a sort of turn based strategy, meets real time strategy, meets fighting! It was so interesting and well done, you could end up spending hours just trying to figure out new strats and different warriors to use to get through a section and either lose as few casualties as possible, or try to lose none at all (very difficult, especially early on). It also had the effect of unlocking various things in the game proper (such as new customization options... another Sidetracked by the Gold Saucer activity in itself). And the best part was if you enjoyed the fighting in the game, it used the conventional fighting of the game (rather than some weird hybrid version as was used in some of the Tekken side games) so it was the best of both worlds!
The rest of the games since at least Soul Calibur 3 (technically the 4th title in the Soul franchise) have had the customization options for making your own personalized fighters, and have tried their hands at additional modes to keep someone entertained beyond just fighting online or with friends, but overall, none were nearly as addictive as the one in Soul Calibur III.
Struggling role-playing game writer Rich Burlew was desperate for a way to draw people into his site, in order to bring more people to his articles and the forums. So he made a webcomic, which has since overshadowed everything else he's done.
Social networking sites get people who socialize for a week or two, then stay for the games.
Users of the Something Awful forums divide into two groups: those attracted by the front page who stayed for the forums, and those who say "Wait, there's a front page?"... and then get probated for being unfunny.
Website/Fark has the same division, created when they offered, for $5/month to be able to see the links that weren't approved for the main page. Folks started submitting links which they specifically didn't want on the main page, just to be able to use the comments sections like a forum (Fark does not have a formal "forum", just a mass of rejected links). From that mass, the TotalFark community was born.
Not to mention dozens of other little splits and subgroups on Google Groups, Facebook groups, #fark (IRC). There's even people who, willingly, spend all their time on the Politics tab. Of a web site. On the Internet. 'Willingly'.
Pat: You're like, the worst person I have known in my entire life. Matt: Well this is fun. Pat: God I hate you so-we're no longer friends.
There has been some complaining by fans of the Source mod for Half-Life 2Zombie Master; while the game ostensibly revolves around the titular Zombie Master-controlling zombies and activating traps like a Real Time Strategy game while the rest of the players try to survive and complete the level, many servers play so-called "minigame levels" that revolve around recreations of games like Donkey Kong or Tetris or make an obstacle course (some of which have unavoidable traps that can only be dodged by faking out the Zombie Master). Complaints have been raised on the official forums over this apparent abandoning of the mod's intent.
The Sprite Casino in Harvest Moon DS and DS Cute. Well, two-thirds of the Casino. The blackjack and poker games can be addictive. The Memory game tends to be ignored.
Invoked in the ActRaiser episode, where Arino spends a disproportionate amount of time in the simulation mode, despite his title as Chief being at risk in that episode should he not complete the game in time.
He also insisted to try to access the bonus levels in Pilotwings. At least the two times he succeeded were quite cool.
Bully has passing all the classes, the arcade games, the carnival games, racing bikes, racing go-karts, boxing, running errands, paper routes, mowing lawns, breaking lawn gnomes, collecting rubber bands and trading cards, and generally messing with people.
"There's a giant iron block over there I wonder if I could mine it... no, no, we don't have time!"
davidr64yt of X's Adventures in Minecraft has a similar problem. Every time he sets out with a specific goal in mind ("I will kill cows and collect enough leather to create a full suit of armor.") he will inevitably get sidetracked into doing something entirely different, such as, in the given example, building a boat and wandering the high seas, ending up in a terrible battle to the death with a spider.
Pretty much every interactive Google Doodle counts. From those that hook you up for hours trying to play a song in them (Les Pauls guitar, Moog's synthsizer), to fun mini-games like daily ones of the London Olympics.
Typing in "Atari Breakout" in a Google image search will result in that very game becoming playable. You might forget why you were searching for a picture in the first place.
Pretty much anybody who goes on vacation in Vegas, really (although that's sort of the point). Particularily notable are the people who play the slot machines they have right in the airport & end up losing their shirts before they even see the city itself.
If you do decide to play the slots (which you shouldn't — they don't provide enough of a return), then at least play the ones nearest the doors; they pay out in lower amounts, but they also pay out more often, to 'hook' people on the way out and get them to turn around.