Some guy who's name you do not know, or have temporarily forgotten, or simply cannot pronounce.
Joe: Oooh, where'd you get that neat little fish?
David: Mr. McWhat'sHisFace gave it to me!
David: That guy with the IMPOSSIBLE TO PRONOUNCE NAME!
Joe: Mr. Hunkingalchavinstintinekalilreo Doddlerbuckleloptisisjoeiscoolapy Gooldehiermerwishingstine?
David: ...Yes, that's it exactly.