Banjo and Kazooie meet L.O.G. (Lord of Games) at the beginning of the game. In their second conversation, L.O.G. makes an obvious reference to Mario:

L.O.G.: Very well then, failures, listen carefully.
Kazooie: Failures? We've been in several games already!
L.O.G.: But nowhere near as many as that Italian gentleman, correct?
Banjo: He does have a point.