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A Gallery is an unlockable feature in Metroid Fusion (Japanese version only), Metroid: Zero Mission, Metroid: Other M and Metroid: Samus Returns. They are always unlocked after the game is completed once, and feature concept artwork of the game in question, or in the case of the former two games, the endings that have been unlocked. The Concept Gallery featured in the Prime Series is similar.
Both of the Game Boy Advance-based Metroid games feature galleries that unlock after completing the game at least once, and include each ending that has been unlocked by the player. This allows them to view the endings at any time, without having to complete the game all over again. The Fusion Gallery is unlockable only in the Japanese version, and can be accessed on the Title Screen. The endings are unlockable by completing the game on Normal and Hard Mode in under certain times and with a certain percentage of the items. Additional endings exclusive to the Japanese version can be unlocked with Child Mode enabled (which enables kanji text). These endings depict moments from Samus Aran's past, such as the attack on K-2L and her training with the Chozo. The five North American endings (which are included in the Japanese version as well) are primarily fan-service, depicting Samus in her revealing Ending Outfit.
Metroid: Zero Mission
All versions of Metroid: Zero Mission feature a Gallery depicting all of the endings. As with Fusion, these endings are difficulty specific and are also intended as fanservice, with Samus wearing another Ending Outfit, as well as her Zero Suit.
Connecting Metroid Fusion on one Game Boy Advance to Zero Mission on another via the Game Boy Advance Game Link cable unlocks a Metroid Fusion Gallery in the latter game containing all of the former's endings, including the Japan-only ones, and two additional endings. These depict a battle between Samus and Ridley in a comic-book style, and a box of Samus, SA-X and baby figures.
Metroid: Other M
Gallery Mode can be unlocked in Other M after completing the game once, and is accessed from the Title Screen like Fusion. Unlike Fusion and Zero Mission, the gallery features concept artwork and not endings, the first non-Prime Metroid game to do so. There are eight pages with 96 pieces of concept art, which is gradually unlocked as more items are collected in a game file. The concept art includes various developer notes written in Japanese, which have been unofficially translated by the Metroid Database (see this link). A rip of the entire Other M gallery can be viewed here.
Metroid: Samus Returns
There are two galleries in the game, the Metroid II: Return of Samus Gallery and Metroid: Samus Returns Gallery. Both galleries become available to unlock after completing the game once, and scanning amiibo. Using the Super Smash Bros. Samus amiibo will unlock the Metroid II gallery, and using the second Samus amiibo specifically created for Samus Returns unlocks the gallery for the same game.
The galleries include concept art from both games. Interestingly, the Metroid II gallery features an art piece of the baby that had never been released prior. It only includes artwork of enemies from Metroid II that were retained in Samus Returns, such as the Mumbo, Autrack and Blob Thrower. Another, separate gallery of artwork, the Chozo Memories, depict the history of the Chozo on SR388 and are unlocked by collecting all the power-ups and expansions in the game.
- "To unlock this collection in the Gallery, you must first beat the game at least once. After doing so, please tap this amiibo again."