Final Egg (ファイナルエッグ,Fainaru Eggu?) is an action stage from the game Sonic Adventure and Dr. Eggman's secret base hidden deep in the jungle of the Mystic Ruins. It is played as the first stage in Gamma's storyline, and is the final stage in both Sonic's and Amy's storyline. E-102 Gamma was also created in the base.
Near the end of the level, there is a particularly slow-moving platform which leads to four extra lives. This was most likely intended as preparation for the battle with the Egg Viper within the level itself. In the final game, the battle was split from the level (so progress is saved), so the extra lives are unnecessary. However, they were possibly left there for the player to discover.
Beyond the capsule, there is an unused tunnel that is blocked off, but it can be accessed using the Light Speed Dash. It was intended to trigger the cutscene for the Egg Viper battle within the level itself. However, in the final game, the battle was split from the level. As a result, a capsule was implemented and the area was sealed off, probably due to the difficulty of the level.
An unfinished duck badnik was intended for this level, but completely removed in the final game. It can be found in pre-release copies, where it shoots at the player and attempts to run away.
A Sonic doll appears in Gamma's story, and he is required to shoot it as commanded by Dr. Eggman. The Sonic doll also appears in Sonic X, where the E-Series use the doll to train within the Egg Carrier.
At the end of Amy's level, where there is a choice of paths, if one were to choose the wrong direction, the monitor changes between an Eggman symbol and what looks like a Poké Ball from the Pokémon series.
In Amy's version of the stage, there is a small section that Sonic does not explore at all in the first act.
Final Egg boss fight
Sonic fighting the Egg Viper as Final Egg's boss fight
A type of robot seen in Final Egg
dolls of Sonic, Tails and Knuckles found in Final Egg