A blumpkin that is performed whilst one or both of the participants is/are role playing as Willy Wonka characters, most notably Oompa Loompas.
Guy 1: Dude did you hit that last night?
Guy 2: Yeah, she totally gave me a scrumdiddlyblumpkin. But now my dick is starting to swell up like a blueberry, and there's orange body paint all over my toilet.
Guy 1: Damn...