Just a Wario Fan
The ίςε cream aficionado
This one sounds like a sampled Wario World song plus the bossfight is something you'd see in Mirror Mansion:
Skip to 0:47
Sounds more like Jungle Hijinx from DKC to me, but given that River City Girls 2 is developed by WayForward, who also made the Shantae franchise whose first game draws a fair share of inspiration from Wario Land, it may not be that unlikely.