In an interview with Gamasutra, director Goichi Suda, better known as Suda 51, mentioned that Takashi Miike, director of insanely violent movies like Ichi The Killer, had a cameo appearance in No More Heroes 2.
GS: Ah, well Miike is pretty busy, so… He has a cameo in No More Heroes 2, though, did you know that?
GS: Well, he’s in there, although it didn’t get reported on much. He does the voiceover as well. Nobody’s asked about that apart from you. It’s surprising how few people know about that.
His Gozu is one of my favorite movies.
GS: I had Miike sign my copy of Gozu.
Look for him at the 4:30 mark.