* AscendedFanon: Sega adopted the FanNickname for Sonic's lycanthrope form.
* CrossDressingVoices: Chip is voiced by a man in English, but voiced by a [[Creator/RyokoShiraishi woman]] in Japanese.
** "Werehog" for Sonic's lycanthrope form started out as this.
** People also call Orbot (Eggman's assistant mini-robot) "Ergo," because [[VerbalTic it keeps using that word]].
** [[spoiler: [[Franchise/PowerRangers Gaia Temple Megazord]] for the Gaia Colossus, the HumongousMecha Chip creates out of all the world's Gaia Temples]].
* GenreKiller: This game's reception was pretty much the final nail in the coffin for fully 3D ''Sonic'' games. Starting with ''VideoGame/SonicColors'', the series would instead adopt a style more like this game's daytime half.
* RecycledScript: While not identical, the plot of ''Sonic Unleashed'' is very similar to that of ''[[VideoGame/SonicAdvanceTrilogy Sonic Advance 3]]'', which was released four years earlier.
* TheOtherDarrin: Surprisingly, in the Japanese version, the Werehog. Creator/TomokazuSeki performs the role instead of Creator/JunichiKanemaru.
** This is completely averted in the English version, where Creator/JasonGriffith voices both Sonic's normal form and his Werehog form.
** Early concept art for Sonic's transformed state was a [[http://www.otakufreaks.com/wp-content/uploads/2009/03/soniclobo03.jpg Yeti]]
** Meta-example here; The Hedgehog Engine was originally intended to be licensed out to other developers. This never happened however, and it appears to have been completely internalised as of the release of ''Generations''.
** This was actually going to be [[WorkingTitle Sonic Adventure 3]], but they couldn't figure out who else to put in the game.