During early development the developers experimented with having each character have a different way of racing, with Sonic running, Dr. Eggman in the Eggpod, and Gilius Thunderhead from Golden Axe riding on top of a Chicken Leg. This idea was abandoned when they found that the gameplay just wasn't enjoyable, mostly due to the racers being different sizes, as well as problems getting characters on foot to drift the same as characters in cars.
Jacky and Akira are the only characters in Sonic & Sega All-Stars Racing to have reused artwork. In this case, their artwork was taken from Virtua Fighter 5

During loading screens, Sonic appears with a "Sonic Says" hint, a reference to The Adventures of Sonic the Hedgehog cartoon.

On the early releases of the game, Sonia appears on a playing card representing the Queen of Diamonds which can be spotted on the ground of the race track, Roulette Road. Sonia's head was taken from a piece of fan art from Deviantart drawn by a user formerly known as Lightning_duchess (now RianaLD). Steve Lycett, Game director commented on the cameo by saying; "We take these things seriously at Sumo and will be contacting the original artist directly to offer our sincere apologies to her, this was entirely unintentional. Not much else I can really add!" This image was only supposed to be used as a place holder.
This is the Last Sonic game to use the 4Kids voice actors, who, with the exception of Mike Pollock, were replaced with the Studiopolis and Funimation voice actors.
Mario was considered for a role as a playable character, however, the developers wanted to avoid cross contamination with the Mario & Sonic series.
Sumo Digital had tried to get Toejam and Earl in the game as well. However they were unsuccessful with obtaining the rights for both All-Stars Racing and its sequel All-Stars Racing Transformed.