The Announcer will express approval when voice volume is increased and anguish when it is decreased in the audio settings.
Contributed by CuriousUserX90
When showcasing the Rogues' Landing racetrack to Skies of Arcadia co-director, Shuntaro Tanaka, Tanaka was reported to sit in complete silence during Steve Lycett's presentation. When the presentation concluded, Tanaka suddenly started crying tears of joy claiming, "It's brilliant - you've perfectly captured what the original game was like. You've made me really, really happy!"
Contributed by SilverSupernova
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General Winter's red Soviet star symbol on his tank was altered due to complaints on the game's official forums due to its apparent visual similarity to the Swastika.
Contributed by ProtoSnake
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Stickers for Hot Wheels and Go Daddy brands can be seen on Danica Patrick's vehicle.
Contributed by CuriousUserX90
When asked about guest characters, similar to Banjo & Kazooie in the original game, Steve Lycett stated that they would prefer to go with characters who aren't tied to a specific company for the sake of including them on all platforms. He goes on to list Bub and Bob from Bubble Bobble, Arthur from Ghosts’n Goblins, Mega Man, and Pac-Man as characters they would love to use under this criteria.

Despite this 'available on all platforms' preference, Lycett added, "Though if I personally had my pick, it’d be Kirby! Everyone knows he is nails!"
Contributed by SilverSupernova
In response to fans requesting additional characters as downloadable content, game director Steve Lycett posted on Sega's official forums, challenging them to organize a vote to nominate characters for him to recommend to Sega. Seven characters were chosen for recommendation, including Ryo Hazuki, Hatsune Miku, Segata Sanshiro, Vectorman, ToeJam & Earl, Bayonetta, and Ristar. On January 24, 2013, Lycett has confirmed that Ryo Hazuki had been approved for development.
Contributed by Tuli0hWut
Segata Sanshiro, the Japanese mascot for the Sega Saturn console, can be seen riding a missile while holding a Sega Saturn console if the player is in the lead on the final lap of "Race of Ages".
Contributed by CathcyJ
Bayonetta was almost selected to be a playable character in the game, but she was left out because the developers thought that including her would affect the game's age rating.
Contributed by Pogue-Mahone