History PermanentlyMissableContent / ActionAdventure

*** A few bestiary entries are permanently missable:
*** The bestiary entry for the Mudman, if you kill the Lesser Demon (boss) without waiting for him to summon a Mudman. While the Lesser Demon becomes a DegradedBoss later on, those only summon more Lesser Demons and nothing else.

** Averted in the UsefulNotes/WiiWare remake. There is one NPC in the game who can reset some of the puzzles if you screw them up after you beat the boss of the Dimensional Corridor.

*** Due to a programming error involving [[EventFlag Event Flags]], once you've acquired the Poacher's Saw in adult Link's ChainOfDeals trading sequence, a Deku Nut carrying capacity upgrade available as child Link in the Lost Woods will become permanently unobtainable if you haven't gotten it yet. Since going for the [[InfinityPlusOneSword Biggoron Sword]] is the first thing many savvy players do upon becoming adult Link, this made HundredPercentCompletion impossible for many. This glitch is fixed in the UsefulNotes/Nintendo3DS remake.

** ''VideoGame/TheLegendOfZeldaTheWindWaker'': Although the game doesn't have any ''material'' permanently missable items, if you want to achieve HundredPercentCompletion on your [[FirstPersonSnapshooter figurine collection]], you need to take a pictograph of everyone alive within the game; enemy, ally, NPC and boss alike. This is alleviated somewhat by the NewGamePlus and the BossRush near Ganon's Tower near the end of the game, but it's difficult to get a photo op of certain subjects (like a random Rito NPC that [[GuideDangIt inexplicably disappears after a plot event]]), so they can eventually become Lost Forever anyway. The VideoGameRemake for UsefulNotes/WiiU averted this for a while thanks to Website/{{Miiverse}}, from which you could receive pictographs (from players ''worldwide'') of the missable targets; but in late 2017, Miiverse itself was shut down.

*** There is a feature where enemies will eventually upgrade to stronger versions of themselves when you kill them enough times. Because their equipment also upgrades, it's possible to lose out on certain weapons to fill out the Compendium, particularly with the Lynels, whose equipment is unique to them. Thankfully, you can buy any missing images for your Compendium from an NPC; you are only missing out on the chance to use or take photos of those weapons yourself.

** And this doesn't even begin to describe the rare and easy-to-miss herbs. There are only a small number of them in the whole game, and you naturally use them when you get low on health. '''Don't'''. You'll need them to fight the BonusBoss.

*** Due to a programming error involving [[EventFlag Event Flags]], once you've acquired the Poacher's Saw in adult Link's ChainOfDeals trading sequence, a Deku Nut carrying capacity upgrade available as child Link in the Lost Woods will become permanently unobtainable if you haven't gotten it yet. Since going for the [[InfinityPlusOneSword Biggoron Sword]] is the first thing many savvy players do upon becoming adult Link, this made HundredPercentCompletion impossible for many. This glitch is removed in the UsefulNotes/Nintendo3DS remake.

* ''VideoGame/{{MetroidPrimeTrilogy}}'' Across the entire trilogy, 100% completion also accounts for enemy and boss scans. While it can be frustrating to forget to scan a boss you can't fight again, each game also seems to have one enemy type that is easy to miss and for whatever reason will not respawn.
** One of the most notorious examples being the Ice Shriekbat in ''VideoGame/{{MetroidPrime}}'', and enemy that divebombs you on sight, leaving little room to scan it, and is a palette swap of a more common Shriekbat, making it difficult to notice this is in fact a new enemy worth scanning before it's gone and exploded itself. The enemy will not respawn after a checkpoint short after its first appearance, making this frustrating; to really turn it into a headscratcher is the fact this was fixed in some later versions but unfixed for the Switch remaster.

** In order to achieve HundredPercentCompletion, you must find and feed every animal (or cluster thereof) in Nippon. Of the hundred or so animals that litter the game, one is missable, which is found during a [[PortalToThePast one-time trip 100 years into the past]]. If you forgot to feed that one dog, you won't get another chance.

* ''VideoGame/CaveStory'' contains numerous easily missable one-shots, many of which are required in order to reach the [[BonusLevelOfHell secret hell level]], which leads to the game's [[MultipleEndings best ending]]. The worst of these moments: if you don't [[spoiler:search the corners of a certain room before triggering a cutscene, or search it after the boss fight and before [[FissionMailed your air supply runs out]], the tow rope, Curly Brace and]] the ability to obtain the best ending are lost forever in one fell swoop. You'd naturally assume that you would want to [[spoiler:save Professor Booster when he falls to the bottom of a pit in the Labyrinth]]. However, if you do that, two items necessary to get the best ending (and one necessary to [[spoiler:save Curly's life]]) are lost. Also, a little bit after that, there's a rest point that can easily be missed, as you are flying past it in a high-pressure stream of water. Even if you followed all of the other steps, if you don't [[spoiler:go into that room, sleep in the bed, read the computer monitor, read the bookshelf, read the computer monitor again, talk to Curly, then talk to her again ''and'' choose to take her with you, she will die and]] you'll miss out on the best ending. Cave Story 3D extended the ledge you need to jump on to make it to the Cabin, however, so it's easier to reach. However, it only gets worse from here: you need to find a hole in the ground in one of the last levels (however, you do need to move past it to advance at one point), and you find out about a mushroom that cures amnesia. To find said mushroom, you have to remember a door near the very beginning of the game that's very possible to look over completely, go through a somewhat confusing questionnaire, make sure the thing you just got is useless, and then you have to fight the mushroom you [[spoiler: feed to Curly to cure her amnesia]]. After you feed it to her, you have to talk to her so that she'll give you the Iron Bond. Then, once you beat the [[spoiler: normal]] FinalBoss, as you [[spoiler: flee the falling island, you have to enter the shed that, in all other scenarios, would be locked, and then jump down the pit in the floor. Better hope you saved.]]

** The compass and map found in the dungeons of ''VideoGame/TheLegendOfZeldaALinkToThePast'' can be passed up rather easily. With all of the main dungeons, a completionist can come back to claim them even after defeating the boss of the dungeon (even though they only have any kind of effect in that dungeon). However, for some reason, the doors to Hyrule Castle will permanently lock themselves up at a certain point, sealing the map[[note]]Hyrule Castle has no compass[[/note]] therein away forever. If you reenter the sewer section using the headstone in the far upper left corner of the graveyard in an attempt to check whether or not you have them it doesn't even show that you have the big key, a required item. So on top of being potentially lost forever, you may never know if you've got it.

*** The DX version on the Game Boy Color has 12 photos to collect throughout the game. Three of these are during the short time that you are with [[spoiler:Marin. Go to the cliff face at the extreme lower left grid space on the map for one, fall down the well 5 spaces above that space, and go to the Rooster statue in town]]. There is also another missable photo where you need to approach a gate to a castle (from the outside) after you start the quest to invade that castle but before you finish the quest, since the gate is opened by a switch so the photo is gone. (If you complete the quest without opening the gate, it is still Lost Forever because the NPC will not check on your "progress" due to it already being over.) There is also a cave not far from the castle that is only visitable with the flying rooster, which will leave you after it's no longer quest-important.

** ''VideoGame/TheLegendOfZeldaOcarinaOfTime'' had a few glitches that rendered some content permanently missable under certain circumstances:

*** It was also possible to render the Piece of Heart obtained by Dampé's "Heart-Pounding Gravedigging Tour" minigame permanently lost if the player leaves the Graveyard without grabbing it after Dampé digs it up. Although, since this Piece of Heart is considered ThatOneSidequest by quite a few people due to being a LuckBasedMission and FakeLongevity caused by Dampé walking at a snail's pace ([[JustifiedTrope justified]] somewhat by his old age), why would you ''not'' pick it up right away?
** ''VideoGame/TheLegendOfZeldaMajorasMask''
*** Before reaching the Clock Tower you'll come across a treasure chest that contains 10 Deku Nuts. While this is extremely minor, it ''is'' the only thing in the entire game (minus Rupees) due to the game's time travel mechanic being introduced after this.
*** A downplayed example occurs with the seahorse side quest at Pinnacle Rocks. If Link completes the Great Bay Temple, the fisherman holding one of them will move to a new location and won't trade the seahorse, even if Link has the thing he wants. Link must reset time to complete this side quest.
*** The Anju and Kafei sidequest relies somewhat heavily on this. Certain elements of it will be rendered permanently missible, at least on that time cycle, until you reset and do it over, depending on what choices you make. Saving the Bomb Shop Owner's Mother from Sakon renders the ''entire thing'' undoable since Sakon never goes to the Curiosity Shop to fence the bomb bag, and thus is never spotted by Kafei, and you can choose to give the Special Delivery To Mama to either the Mailman to deliver or directly to Madame Aroma herself: the former earns you the Postman's Cap, the latter earns you a Bottle of Chateau Romani.
** Although ''VideoGame/TheLegendOfZeldaTheWindWaker'' doesn't have any ''material'' permanently missable items, if you want to achieve HundredPercentCompletion on your [[FirstPersonSnapshooter figurine collection]], you need to take a pictograph of everyone alive within the game; enemy, ally, NPC and boss alike. This is alleviated somewhat by the NewGamePlus and the BossRush near Ganon's Tower near the end of the game, but it's difficult to get a photo op of certain subjects (like a random Rito NPC that [[GuideDangIt inexplicably disappears after a plot event]]), so they can eventually become Lost Forever anyway. The VideoGameRemake for UsefulNotes/WiiU averted this for a while thanks to Website/{{Miiverse}}, from which you could receive pictographs (from players ''worldwide'') of the missable targets; but in late 2017, Miiverse itself was shut down.

*** Similar to above, there is a feature of the game where enemies will eventually upgrade to stronger versions of themselves when you kill them enough times. Because their equipment also upgrades, it's possible to lose out on certain weapons to fill out the Compendium, particularly with the Lynels, whose equipment is unique to them. Thankfully, you can buy any missing images for your Compendium from an NPC; you are only missing out on the chance to use or take photos of those weapons yourself.

** Speaking of Void Heart, you ''cannot'' access the first ending (''Hollow Knight'') after you have it, as the final stage of the FinalBoss fight is replaced by the sequence of events that lead into the second and third endings.