Are separate characters, but the vehicles are very similar. So similar shape, but different colors and decorations. This is because Reala, Gum and MeeMee were developed after the original roster was decided. Sumo made it sound like they put extra time into the extra racers in order to beef up the roster and give fans more racers to choose from. Of course, to save money and time they based the secondary character vehicles on their counterpart's vehicles.
Although I don't mind the extra racers in the game, I don't 100% agree that Sumo went out of their way to do this for free, per se.
I do reckon that they had enough time to add them and asked SEGA if they can reuse the characters because they were well within the time frame to release the game.
I mean, it's still great that they did that but yeah...I don't believe they did it for free.
Anyway, the new Wii U trailer shows off the Billy Hatcher track.
It reminds me of Christmas Town and I really did go "WHAT'S THIS!?! WHAT'S THIS!?! It looks like Christmas Town. What's this? Billy Hatcher still not found?" XD