Anticlimax Boss: Unless you're really playing with the worst possible duo to fight that boss. Kabutops and the Omastar brothers in the Brine Cave are dramatically hyped-up in-story as "vicious Pokemon" that Chatot and Wigglytuff barely managed to survive encountering in the past. They also take out Team Skull effortlessly. They all happen to be Rock/Water types though, so if you or the partner is a Grass type, the battle is pathetically easy. Even some Fire type starters can win the battle without much difficulty, especially if they're able to exploit the Rock type of the ennemies, for example with Fighting-type moves (Focus Punch can deal massive damage to them, if not one-hit-kill the Omastar brothers.
Complete Monster: Darkrai serves as the true Big Bad, and is depicted as far more evil than Classical Darkrai. He was responsible for the collapsing of Temporal Tower that lead to the Bad Future, tortures an innocent child with violent nightmares to lure out the Player Character and their partner, and makes several attempts to assassinate them so he can try his plans again. One of his most heinous acts involves trying to have the heroes willingly commit suicide by tricking them into thinking their existence is threatening the space-time continuum due to time travel shenanigans. A Manipulative Bastard par excellence, he has no regrets for his crimes and wishes nothing more than the complete and utter destruction of the world, just so he can rule the tattered remains.
Critical Dissonance: Critics gave it a tepid-at-best reception. Fans on the other hand have given it Cult Classic status for its powerful and moving story, and it is widely considered to be among the best Pokémon spinoffs.
Cult Classic: Due mainly to its narrative and a soundtrack brimming with great music, this side-game has almost as many fans as any entry of the main Pokémon series, and it still remains a popular and well-regarded game even years after its debut—if anything, after some Contested Sequels in both the main franchise and the Mystery Dungeon subseries, it's gotten more popular with time. Sky in particular is well-regarded for adding in the Special Episodes, increasing the number of playable Pokemon, and letting players experience the soundtrack whenever they want with the Sky Jukebox.
Purugly in the Hidden Land. They have Fury Swipes, which is already annoying when you consider multi-strike moves are Game Breakers, and Swagger, a confusion-inducing move that boosts your attack so you're likely to miss or hit your allies.
Pretty much ANYTHING in Temporal Spire. Specifically, the Porygon-Z who have Discharge which will hit you no matter where you are for really high damage which you likely won't be resistant to, and use Agility to boost the speed of every enemy in the room, meaning a Mighty Glacier like Salamence will now hit twice as fast. Salamence and Metagross also hit like trucks and if you're weak to Psychic, Dragon, Steel, or Fighting, you'll die really quickly to Bullet Punch, Psychic, Dragon Claw, and Meteor Mash respectively.
Ear Worm: Aegis Cave. It doesn't help that Aegis Cave is the setting for a particularly time-consuming and tedious mission.
Although both Explorers and Rescue Team were received about the same by critics (that is, lukewarm), most fans agree that Explorers has a better storyline and character development. Rescue Team had a decent, if slightly unoriginal premise of natural disasters and a rather bland supporting cast. Then Explorers arrived, with the player's status as a human and their own character being far more important, a more fleshed-out and unique supporting cast, and a wider variety of Pokémon as prominent characters even with the expected focus on Sinnoh Pokémon.
Doubly so for the Sky version, which averts the One Game for the Price of Two elements from Time and Darkness, brings more starter Pokémon, adds a handful of side-stories for more character depth, and introduced a few aspects that, much to the chagrin of the fanbase, weren't used again in future sequels, like the Spinda Bar and the Lookalike items.
Primal/Dark Dialga is widely remembered among the fanbase, particularly after the release of Omega Ruby and Alpha Sapphire, which introduced Primal Groudon and Kyogre (Primal in both versions, as oppose to English only), as this opened up the thought of the cover legends of the next set of remakes in line - the Sinnoh games - having the Primal forms from this game.note Primal Palkia doesn't exist, but the fanart alone speaks volumes.
Fridge Logic: In a world where the sun never shines, the water doesn't flow and the seasons are non-existent, how do the native Pokemon stay alive when their food sources are frozen in time and thus can't grow anything?
Maybe Celebi uses the Passage of Time to travel to the past and get whatever food and water they need.
Apples, berries, and seeds randomly generate in the future dungeons just as well as they do in the past dungeons. Whether or not this is some kind of weird Gameplay and Story Segregation may be up to interpretation, though.
The randomly generated food in dungeons would give inhabitants of the Bad Future some things to eat, but since food still isn't quite plentiful, it's very likely that starvation is an issue for many Pokemon. Notice that in the dungeons in the future, nearly 1/3 of the encountered enemy species are Ghost-type...
Good Bad Bugs: Occasionally, when winning big at the Recycle Shop, the prize is a higher tier ticket. You can receive and redeem it even if the shop doesn't offer the tier yet.
He's Just Hiding: A fair portion of the fandom's reaction to Grovyle's disappearance near the end of the main arc. What actually happened to him was later revealed in Special Episode 5 of Explorers of Sky.
Harsher in Hindsight: Darkrai revealing how the player and Grovyle were separated. Darkrai attacked them returning to the past, and the player was separated after they shielded Grovyle from the attack. The scene made harsher is Grovyle's Heroic Sacrifice against Dusknoir, where he similarly shields the player and then is forced to separate himself permanently from his partner. Hammering the point home is both characters using the same boss theme.
In Sky, most evolutionary families get a 3-star exclusive item that, when in the inventory, has the Pokemon healed by damaging moves of a certain type, instead of taking damage. Said type is usually one that would deal super effective damage otherwise, but there are exceptions. One of such is the Bronzor evolutionary family, who get healed by Ghost-type moves, which dealt neutral damage to themnote Because of the way Abilities work in these games, they had no "normal" weaknesses.. Fast-forward into Generation VI, and now Bronzor and Bronzong are indeed weak to Ghost-type moves thanks to the changes in the type chart.
Two localization-only examples. Koffing, Zubat and Skuntank's team was named "Team Skull" in the English version, which ended up being the name of the villainous team in Pokémon Sun and Moon. Similarly, "Primal Dialga" (who was called Dark Dialga in Japan) became this after the remakes of Pokémon Ruby and Sapphire introduced Primal Reversion.
Dusknoir. Pursuing the player and Grovyle into the past, he poses as a friendly explorer using his knowledge of the future in order to pick up information. He successfully deceives Treasure Town into helping him capture Grovyle, thereby dooming the future to paralysis, and even drags the amnesic player back to the future just in case they regain their memory (this one is more implied). Once Grovyle, the player, and the partner escape, Dusknoir allows them to find Celebi, intending to capture her once she reveals herself, even going as far as to bring Primal Dialga to accompany him, and the party only barely escape him. Despite his ruined reputation, he lies in wait in the past in the Hidden Land, and almost captures the party again, forcing them to slow him down with his Weaksauce Weakness and Grovyle to sacrifice himself by dragging them both back to the future. Once back there, as revealed in Sky, he plots to Grand Theft Me Grovyle, a plan he pulls off almost flawlessly until the conscience he'd developed convinces him to stop.
Bar none, Darkrai. Their gambits are utterly ridiculous, so let's recap. Goal, create a world of darkness to rule. Step 1, sabotage Temporal Tower, worked flawlessly to the point of occurring in one timeline. Grovyle and the player tried to stop it, and Darkrai attacks them within the Passage of Time, severely limiting their plan when it gave the player amnesia and transformed them into a Pokémon. Despite this, they still fix time. Plan 2, create a the world of darkness by distorting space. Problem: Space works differently (it doesn't drive Palkia crazy like time did for Dialga), and Palkia averts The Gods Must Be Lazy. Solution: blame the player and partner, who genuinely distort space with their presence, thus getting Palkia on their tails. When his ruse is revealed, he retreats to Dark Crater, and puts the player in an illusion to convince them to join him. When that fails, he revels an army of six other Pokémon to help him. Then when THAT fails, he has a dimension hole ready for a getaway, though unfortunately for him, Palkia finally caught him.
Paranoia Fuel: A conversation with your partner about killing yourselves ends abruptly as the two of you go to sleep. When you wake up, your partner's bed is empty.
Player Punch: The ending of Special Episode 2 in Sky, Igglybuff the Prodigy. Igglybuff has befriended his loyal, trustworthy master (a retired explorer), they've explored and found heaps of treasure. Then, after they beat a remote dungeon, Igglybuff's friends and parents turn up to reveal that Igglybuff's mentor, Armaldo, is actually a B-rank outlaw. You can practically see Igglybuff's world ending as Armaldo's taken into police custody. Can be considered a Bittersweet Ending as well, due to Armaldo's changes in his behavior hinting that he legitimately wants to clean his slate at the end, after spending so much time with a child like Igglybuff. The ending of the chapter all but spells it out.
Rescued from the Scrappy Heap: Most of Chatot's detractors (especially over the Perfect Apple incident) were rather impressed by his actions in the Brine Cave.
Scrappy Level: Who in the hell thought the Aegis Cave challenge was a good idea? At some point in the after the end, your team will be required to go to a dungeon called Aegis Cave. To get through, you must solve three word puzzles by spelling out ICE, STEEL, and ROCK. In order to do this, you must go through each dungeon and fight multiple Unown who might drop a corresponding letter stone for you to spell these words with. Might. You will inevitably have to go through each of these dungeons multiple times to get the correct letters. And this challenge is mandatory. Best part? If you want to go back to recruit the legendary golems, you have to spell out the words all over again. And you might not even recruit them on the first try. However, you can use an online Wonder Mail Generator to get codes for jobs that will get these items. It's still annoying, but better then what you have to do otherwise.
Sequel Displacement: While not as bad as some examples of this trope, some believe that Explorers of Time/Darkness/Sky were the originals and don't know about Red/Blue Rescue Team or just ignore them.
Tear Jerker: The ending cutscene. All of it. Your character disappears before your partner's eyes, leaving them staggering towards the Rainbow Stoneship alone. Several months later, they find themselves on the very beach where they first met you...and end up breaking down in tears after remembering all the adventures you had.
Final Boss Primal Dialga is notorious for being one of the hardest final bosses in the series. His typing is very strong defensively (Dragon/Steel is only weak to Fighting or Ground, which are moves that are rather hard to come by unless you're Riolu), at Level 48 he's liable to be several levels higher than you, he packs a ton of HP and decently powerful attacks, and he has the Intimidator IQ Skill which has a chance to cause your Pokemon's close-ranged attacks to fail. But worst of all, he has Roar of Time, a deceptively accurate move that deals absolutely ludicrous damage and hits the whole map, meaning he can dish out One-Hit Kill attacks before you can even approach him. The upside to this is that he will leave himself vulnerable for the next turn, but expect him to spam it nearly every turn he has it up. You better hope you brought a ton of consumables and Reviver Seeds, because if you lose you have to clear Temporal Tower again.
Palkia in the postgame can be troublesome if he feels like spamming Spacial Rend, which like Roar of Time hits the whole map, deals obnoxiously high damage, and being a Dragon-type move is resisted only by Steel-types.. Unlike Dialga's Roar of Time, however, he doesn't have to spend a turn recharging. Oh, plus he's reasonably bulky and due to his typing he's only weak to Dragon (Fairies weren't introduced yet), making it nearly impossible to hit him for supereffective damage.
Darkrai as the True Final Boss. Being the scumbag he is, he traps you in a seven-versus-three battle. While his team consists of himself and 6 fully-evolved Pokemon, you on the other hand have to deal with Cresselia, who is usually useless, has horrendous AI, and has a weakness to Darkrai, meaning that she will usually run into battle and get herself knocked out in less than three turns. The main way to mitigate this is either to stock up on Reviver Seeds or take out Darkrai as soon as possible, since Cresselia can safely tank the majority of the other minions. This, by the way is easier said than done.
Temporal Tower (and by extension Temporal Spire) may perhaps hold one of the most punishing difficulty spikes in recent years thanks to a myriad of reasons. The penultimate stage of the main story is long as hell and filled to the brim with deadly traps and enemies (most infamously Porygon's evolutionary line that will constantly spam Agility and Discharge), not to mention it only allows you and your partner in, meaning if either one of the two are any sort of weak to the many traps and strong Pokemon in the dungeon, then grinding for experience or for items will be the norm until a winning combination has been made.
Any of the Legendary dungeons, i.e. Bottomless Ocean, Giant Volcano, etc.
Mt. Bristle can be a bit of a challenge for the sole reason that you're not quite strong yet. It's not helped by the fact that Drowzee might be a bit of an Early-Bird Boss, if you get unlucky and his Forewarn ability activates a lot or if you or your partner are weak to psychic attacks.
Treeshroud Forest. It's a very long forest with a variety of Pokemon types (mostly psychic) that hit HARD. And it's long but not as long as Hidden Land or Temporal Tower but it's different in the fact that it has 20 floors...And no Kanghastan Rock in the middle of it. You have to brave 20 floors of nonstop barrages of Pokemon and traps to the end. One can only hope that they still have items in their Kanghastan storage rock at the beginning of the forest, as they had just had the standard chain of dungeons without a visit to the Hubworld that they tend to have in the PMD series.
Dark Crater. Even if you didn't have to escort Cresselia...it's the Final Dungeon. It's long, the Pokémon are powerful, and at this stage type advantage is more needed than ever.
Quicksand Cave can be brutal for the first time through. Just like Northern Desert, there are two food sources in the dungeon, one of which being Grimy Food. Sandstorms regularily appear on floors, which allows Sandslash to avoid most of your moves because of Sand Veil. The other half of the dungeon, Quicksand Pit, is even worse, as past a certain points, Hippopotas start to show up, which means guaranteed sandstorms on each floor. And then at the end, you have to fight Mesprit, who despite being only level 18, hits surprisingly hard with her psychic type moves, which can also end up hitting even harder if you or your partner are Fighting-Types. Bringing lots of food and Reviver Seeds is key to getting through this dungeon without tearing your hair out.
They Wasted a Perfectly Good Character: The role of Giratina. You would think that Giratina would be the game's True Final Boss, what with being the Pokemon stronger than both Dialga and Palkia, as well as having a pre-established relationship with Dialga, Palkia, and Arceus. Obviously, if the game were to have a greater villain, Giratina would be the one, right? Nope, Giratina is a mere treasure-guarder, while Darkrai, a lesser legendary with the same stat total as Goodra, no relation to Dialga/Palkia/Arceus beyond the one movie, and no plausible way to overpower the likes of Dialga is the True Final Boss. To be fair, Darkrai being unrelentingly evil was VERY well-received. In fact, when you recruit Giratina and talk to him in Spinda's Cafe, he's a perfectly friendly guy and more than willing to help out in your adventures. Not exactly Ultimate Evil material...
Tier-Induced Scrappy: Cresselia is perhaps the worst when it comes to this. Not only do you have to escort her to the end of the dungeon (which contains tons and tons of lava for her to float over and burn herself with), but she also takes place in the final battle against Darkrai. That being said, she at least has the Lava Evader IQ Skill, so she won't go onto the lava on her own.
What Do You Mean, It's for Kids?: You learn at the end of the game that you are essentially on a suicide mission, before that you're almost executed, Sky sees Grovyle get tortured...basically everything related to the Bad Future.
The partner, after the player disappears. Or them in general? For one, they're a young Pokemon (presumably a kid) who's also a coward who only got the strength to join the guild from the player, they've gone without dinner because of Team Skull, they were bullied by Team Skull in general, and their best friend/life partner disappears into light before their eyes, leaving them to go home alone while barely being able to hold themselves together. Things seem to be looking up for them when they return, only to have Cresselia (actually Darkrai in disguise) tells them to kill themselves along with the player because they are an anomaly. Ouch.
The Player themselves. For starters, they're an amnesiac from the future who has lost their family and turned into a Pokemon. Especially when finding out they exist only because of a Bad Future and they'll disappear once Primal Dialga is defeated.
Pretty much everyone from the Bad Future could qualify. Grovyle for being an idealist who wants to change the past even if it means he won't exist, Celebi for using most of her energy to send Grovyle, the player, and your partner to the present day and risking being murdered by Dusknoir's Sableye. It only gets worse after the post game story where Cresselia (actually Darkrai) asks you and your partner to kill yourselves to save the world, you're hunted by a well-meaning Palkia, and nearly killed by Darkrai in a nightmare when you dare to interfere with his plans.
Manaphy could also qualify, being a baby who ended up living away from his adoptive parents (you and the partner), and missing the sea despite the fact he enjoys being with you. Fortunately, he returns once he's grown up enough.