Waluigi has the most spirits in Smash out of any non-playable character and runs the gamut of being both a Normal type and a Grappler type.
Grappler types have also been associated with intelligent characters such as Dr. Crygor, Dr. Eggman and Tails. This might also be a reference to Waluigi's association with the mechanical.
Soooo, when will the highly anticipated but already legendary game Waluigi's Taco Stand finally be a real thing? We've been waiting long enough, haven't we?