Luminario
Smash Lord
Yeah, DK being considered a guest character is an unusual thought. I'd say that characters should be added to Mario Kart as long as they belong to the extended Mario franchise, which includes Yoshi's, Wario's and DK's series, and as long as they don't go overboard with the characters. For instance, DK should be able to bring Diddy, Dixie, Funky, and MAYBE K.Rool before it gets too much, so they would have to have importance in their own series. Series that are not related to the Mario universe at all, like Zelda and AC, should however be limited to at most 2 characters. Characters like Shokora, who have barely any chance of appearing anywhere else, could just be assimilated into the Mario Kart roster instead of being brought over as a guest character, especially if they add something to the roster no one else has (for instance, Shokora could be in her true form, bringing a rather androgynous woman to the female side of the roster) but that's just how I feel about this subject.I guess I never considered Donkey Kong characters, including Donkey Kong himself, as guest characters in Mario spin-off games. It just seems odd to consider them "guests", especially when Mario and Donkey Kong and their shared universe originated from one arcade game.
Speaking of shared universes, I would love to see more Yoshi and Wario characters in Mario Kart as well. Kamek, Toady, Poochy, Stork, Bandit, Crazee Dayzee, Raphael the Raven, Captain Syrup, Mona, Ashley, Princess Shokora, and Queen Merelda would be great.
What would the baby characters be in the Mario Kart roster then? would they be Yoshi guests?