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[[quoteright:350:[[VideoGame/Sonic3AndKnuckles http://static.tvtropes.org/pmwiki/pub/images/ChaosEmeralds_1761.png]]]]

[[VideoGameTropes Video games]] have {{Bonus Stage}}s that shower the hero with [[ScoringPoints points]] and [[VideoGameLives lives]], but some games go further, and place optional {{Mac Guffin}}s deep into their bonus stages. The reward for the player that hunts them all down is often a GoldenEnding or [[VideoGameRewards other reward]], but the game can be completed without them.

Usually, a bonus stage can be replayed if the Bonus Stage Collectable in it was missed the first time, but since there are limited opportunities to play the bonus stage, collecting all of the Bonus Stage Collectables is never a guarantee.

In a few rare instances, the Bonus Stage Collectables are actually hidden within the basic levels.

Most popular with side-scrollers on the 16-bit era, particularly on the UsefulNotes/SegaGenesis[=/=]Mega Drive which had battery save on far fewer games.

SubTrope of GottaCatchThemAll, which is a Sub Trope of PlotCoupon.

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!!Examples where they can be {{Permanently Missable|Content}}:

[[foldercontrol]]

[[folder:Franchise/SonicTheHedgehog]]
* ''VideoGame/SonicTheHedgehog'' has six Chaos Emeralds, each with its own special stage, which can be accessed by having at least 50 rings at the end of certain levels. If an emerald is missed, the special stage can be replayed after playing the others, but there are only 10 chances total. Collecting them all slightly changes the ending. The 8-bit version doesn't have Chaos Emeralds in the special stages; they're hidden in the regular stages instead.
** ''[[VideoGame/SonicTheHedgehog2 Sonic 2]]'' has seven emeralds. This time, special stages can be accessed through any checkpoint, leading to the potential for a lot of special stage attempts, but in practice it's tricky outside of the [[GreenHillZone first]] and [[BreatherLevel fourth]] zone. Aside from changing the ending, this game let you turn into Super Sonic with 50 rings, which meant [[GameBreaker high speed and invincibility]] at the cost of rings. The 8-bit version of this game also has the Chaos Emeralds hidden in the regular stages instead.
** ''[[VideoGame/Sonic3AndKnuckles Sonic And Knuckles]]'' (without lock-on) has a limited number of big rings hidden throughout the game which each give one chance at an emerald. In addition to Super abilities for Sonic & Knuckles, a final, secret stage can be unlocked if the emeralds are collected as Sonic. However, as mentioned later, locking ''Sonic 3'' onto the cartridge allows for battery saves, and infinite shots at the challenging special stages.
** ''VideoGame/SonicCD'' has Time Stones in the Special Stages; no Super Sonic, but getting them all and finishing the game will result in the good ending. Interestingly, there's an alternate way: if you destroy the generator found in every level's Past version, you get the good ending without needing the Time Stones.
** Later 8-bit Sonic games such as ''[[VideoGame/SonicTheHedgehogChaos Sonic Chaos]]'', ''[[VideoGame/SonicTheHedgehogTripleTrouble Sonic Triple Trouble]]'', and ''[[VideoGame/SonicBlast Sonic Blast]]'' require the emeralds to be obtained within special stages, much like the 16-bit Genesis/Mega Drive games. ''Chaos'' and ''Triple Trouble'' each have six emeralds (with five hidden in special stages and the sixth having to be recovered from the final battle with Robotnik) and ''Blast'' has five. Collecting all the emeralds in ''Blast'' grants players access to the true final battle with Robotnik.
** Later Sonic games, with a few exceptions, tie the collection of Chaos Emeralds to the plot, turning them into straight {{Plot Device}}s.
[[/folder]]

[[folder:Side Scrollers]]
* ''VideoGame/{{Ristar}}'' has a bonus stage in every level, each with its own treasure. There's only one chance to get each treasure (and only if the bonus stage for that level is found). More treasures reveal more secret codes at the end of the game.
* ''VideoGame/CoolSpot'' has UNCOLA letters (VIRGIN in the genericized European versions). You need a certain number of [[LawOfOneHundred spots]] (depending on the difficulty) to play the bonus round after each level, and hopefully get a letter. The best outcome is to collect and keep them all, but they can be turned in for a continue each.
* ''VideoGame/DynamiteHeaddy'' has seven unmissable (though skippable) opportunities for an intermission bonus stage. It needs to be cleared four times (after which it stops appearing) to get a combination number (which is re-randomized every time you start a new game) for use at the end of the game, which allows you to fight a BonusBoss if entered correctly.
* The Sega Genesis/Mega Drive version of ''[[VideoGame/RocketKnightAdventures Sparkster]]'' has the seven Holy Swords, which are similar to the Chaos Emeralds from the aforementioned ''Sonic the Hedgehog'' games. Like the 8-bit versions of ''Sonic 1'' and ''2'', the swords are hidden within certain stages. Collecting all seven swords allows the player to face the final boss as Gold Sparkster, similar to Super Sonic.
* ''VideoGame/ToeJamAndEarl Panic on Funkotron'' uses this trope, though the "collectables" aren't shown to the player. If you get all the presents in a Hyper Funk Zone, the game counts it as a perfect run. Two perfect runs changes the layout of the Hyper Funk Zone. Two more changes the layout again. Two more perfect runs will award you with unlimited superjars for the rest of the game.
[[/folder]]

[[folder:Turn Based Strategy]]
* In ''[[VideoGame/FireEmblemElibe Fire Emblem: The Binding Blade]]'', the Bonus Stage Collectables are found in the form of the eight legendary weapons. The eight legendary weapons must be obtained from completing [[BonusStage side-story chapters]], bonus levels that can only be accessed if the previous normal chapter has all its hidden objectives fulfilled (such as completing the level before an X amount of turns have passed, keeping specific units alive, etc.) upon completion. To progress to the final arc of the campaign and gain access to the GoodEnding, you must obtain all eight of these weapons AND keep them (as well as the SwordOfPlotAdvancement and [[CuteMonsterGirl Fae's]] weapon) intact (they must have at least 1 charge left) before completing Chapter 22. (Obviously, Fae also needs to be alive.)
[[/folder]]

[[folder:Action Adventure]]
* ''VideoGame/PrinceOfPersiaWarriorWithin'' has optional, hidden life upgrades spread across the game. Finding all of them is necessary to obtain the [[InfinityPlusOneSword Water Sword]] which leads to the game's TrueEnding.
[[/folder]]

[[folder:Miscellaneous Games]]
* The ''VideoGame/{{Glider}} PRO CD'' house "Nemo's Market" puts all but the last of its [[StarShapedCoupon Magic Stars]] in "Shopping Spree" bonus rooms which teleport the player out after the time limit expired, making the house UnwinnableByDesign if even one star is missed.
[[/folder]]

!!Examples where bonus rounds can be replayed infinitely:

[[folder:Side Scrollers]]
* ''VideoGame/DonkeyKongCountry''
** ''VideoGame/DonkeyKongCountry2DiddysKongQuest'' and ''[[VideoGame/DonkeyKongCountry3DixieKongsDoubleTrouble Dixie Kong's Double Trouble!]]'' have unusual examples. You get bonus coins for completing the bonus stages, and these are required to get into the [[BonusDungeon Lost World]].
** ''VideoGame/DonkeyKongCountryReturns'' and ''[[VideoGame/DonkeyKongCountryTropicalFreeze Tropical Freeze]]'' fill the bonus stages with normal collectables like bananas, but collect all of them and you get a puzzle piece, of which there are only a few per level and are needed to get HundredPercentCompletion.
* ''Sonic 3'' (and by extension ''VideoGame/Sonic3AndKnuckles''). Unlike the other old Sonic games, this one has a battery save, so getting all the emeralds is a matter of time and persistence.
** Most new Sonic games use the Chaos Emeralds as straight-up {{Mac Guffin}}s. ''VideoGame/SonicHeroes'' is an exception where they follow this trope. There are keys in cages in various... [[GuideDangIt interesting]] locations throughout the stages. A Power character breaks the cage, and once the cage was broken the key just has to be picked up like a ring or some such. Losing your rings means losing the key (due to this, people usually use Team Rose, the game's "easy mode"), and getting to the end of the stage with the key gets you into the special stage after it adds up your score. You can only get the Chaos Emerald if you get the key in the second stage of any theme (basically, second act) - the first act just gets you points and lives. Getting all the Emeralds and completing the story for every team unlocks the Last Story (TrueFinalBoss and the true ending).
** In ''VideoGame/SonicColors'', it's actually impossible to get the Emeralds the first time through, due to the complicated procedure required to get them. First, you have to start collecting lots of special rings, of which there are five in each Act. You can start getting Emeralds once you have at least 120 of them; you need all of them to get all the Emeralds. [[DoubleUnlock Then]], you have to finish the Sonic Simulator stages unlocked by the special rings; completing all 3 in a group (for example, 1-1, 1-2, and 1-3) unlocks one Emerald. The reason it's impossible to get all the Emeralds the first time through is because some of the special rings in earlier Acts can only be reached by using Wisps unlocked later on. Getting all the Chaos Emeralds doesn't affect the story, but it does unlock the ability to play as Super Sonic; however, [[AwesomeButImpractical this disables Wisp powers]] (sometimes tweaking level layouts correspondingly), so it's more of a BraggingRightsReward.
* 6 hidden items in ''VideoGame/IWannaBeTheGuy'' serve this purpose, as collecting them all just unlocks the BossRush. However, only one of them is PermanentlyMissableContent, being stuffed away in the ''VideoGame/{{Metroid}}'' section.
[[/folder]]

[[folder:Platformers (3D)]]
* ''Franchise/CrashBandicoot''
** In ''Videogame/CrashBandicoot1996'', collecting tokens of a particular character will take you to a Bonus Round that lets you save (a rare commodity). In particular, the Cortex Bonus Rounds will reward you with a Key when you get to the end, allowing you to access secret levels.
** ''Videogame/CrashBandicoot2CortexStrikesBack'' and ''VideoGame/CrashBandicoot3Warped'' feature Death Courses, unlocked by making it to the relevant platform mid-way in the level without dying. Make it to the end and you're rewarded with a Gem; however, unlike Bonus Rounds, dying in the Death Course will cost lives. Coloured Gems will unlock further platforms, a few of which also reward you with a Gem.
* ''VideoGame/ElShaddaiAscensionOfTheMetatron'' has the Bones of Ishtar hidden in a bonus level, which unlock the game's best armor. The risk is ramped up since while DeathIsASlapOnTheWrist in normal gameplay, there is a permanent death when playing those levels.
[[/folder]]

[[folder:Puzzle Games]]
* ''VideoGame/DeadlyRoomsOfDeath: The Second Sky'' rewards solving bonus levels with an RCS stamp. When the GlobalAirship is unlocked near the end of the game, each RCS stamp unlocks an additional bonus level. The GlobalAirship also allows you to return to earlier bonus levels, so none of the stamps can be [[PermanentlyMissableContent lost forever]].
[[/folder]]

[[folder:Other]]
* ''VideoGame/{{Pickory}}'' features various "secret items" to collect, most of which are hidden in optional secret levels. They don't unlock anything, so it's just for the extra challenge.
[[/folder]]
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