Fridge Logic: One of the earlier Event Matches Missions, You play as Amigo in a mission titled "Mardi Gras". Amigo is a mexican partying monkey. Mardi Gras is a french holiday. What the hell man?
Mardi Gras is essentially considered the Holiday of Partying. Amigo is a party monkey. I mean, this ain't Bastille Day.
Fridge Logic: Why the heck is Metal Sonic playing Metallic Madness Present whenever he goes into All-Star? Wouldn't the devs have found it to be more fitting, considering the context, to play Stardust Speedway (any version at all) instead?
Fridge Horror: Metal Sonic has a skeleton. At first, it doesn't make sense, but when you realise what Eggman originally put in his robots to power them...
Fridge Brilliance: Technical reasons aside... why is Sonic driving a car? Well, being the fastest thing alive, he would be disqualified if he were on foot. Plus, considering the nature of the races in the sequel, he would not be able to keep up on water or above ground.
Sonic Lampshades this in Sonic Universe #45 after being asked why he has to drive; he finishes the race in a millisecond on foot, answering that question.
Similarly, Beat, being that he can apparently skate as fast as his car, would probably also be disqualified for being on foot if he didn't save his skates for his All-Star, and that he probably can't skate in the air or the water for Transformed.
Additionally, it's been established that Sonic likes to play fair and will ratchet himself back a bit or abide by the rules in the name of sportsmanship. He stuck to Extreme Gear for the Ex-World Grand Prix, of course he'd hop in a car for this.
Also, it's very hard to drift on foot.
And, for Transformed, Sonic cannot swim or fly. He needs that shifting car to remain in the races. Opa-Opa is perhaps the only protagonist of a SEGA game able to travel in all three ways without a vehicle to help. Which is what makes Opa-Opa's removal in Transformed itself mindboggling.
Except that the first Sonic & Sega All-Stars Racing also had Mii, Avatar and Banjo-Kazooie.
Mii and the Avatar are both additional characters that allow you to race as yourself, and not necessarily franchise characters. Rareware is now owned by Microsoft and was specifically asked to be put into the game.
Also, the the game is specifically labeled "Sonic & Sega All-Stars Racing With Banjo-Kazooie". Banjo and Kazooie are made seperate from the Sega characters in the title. So if the sequel still had "Sega" in the title, then it would've been "Sonic & Sega All-Stars Racing Transformed With Wreck-It Ralph and Danica Patrick", or on the PC version, *deep breath* "Sonic & Sega All-Stars Racing Transformed With Wreck-It Ralph, Danica Patrick, Pyro, Heavy, and Spy".
The most reasonable reason would be simply to avoid Overly Long Title. Sonic & Sega Allstars Transformed is a mouthfull...
So Wreck-It Ralph is in Sonic & All-Stars Racing Transformed in exchange for Sonic's cameo in Wreck-It Ralph. That's fine. But why isn't Vanellope, canonically a kart racer in her own (fictional) game, also in this game? Even if they only added the one character (Ralph) out of contractual obligation, it seems like a missed opportunity.
Not everyone is familiar with Vanellope yet.
This could also be one of Ralph's "game-jumping" adventures.
One of the people from Sumo Digital said it was because they only wanted to have one Wreck-It Ralph character. It's also most likely because it would spoil the fact that by the end of the movie, Vanellope becomes part of her game's code again, and is therefore able to game-jump with the others. Keep in mind that when this game came out, the movie had just been released in American theaters, but European theaters wouldn't get the movie until February 2013.