-Specials-
Stanley: Smoke screen. He'd pull out his sprayer and obscures a portion of the track with a thick cloud
DK junior: One of those mechanical clap-traps. It'd bury itself in the ground and snap at a kart that run over it.
Buzzy/Spiny: One of its respective species. It aimlessly wanders the track, like Bowsers fireballs from the first game.
Geno: Geno Blast. A extremely large, but slow attack lowers downwards towards the track. Will you try and drive around it, speed up and just avoid it, or maybe even hit the brakes?
Mallow: That star spell that'd function somewhat to the Geno blast but faster, more repetitive, maybe smaller, or a Rain spell that causes parts of the track undriveable.