From the "King Yakko" episode (09/24/1993) of animated television series Animaniacs . Voiced by Jeff Bennett, even though Spinal Tap actors Christopher Guest and Michael McKean guest-voiced the villains Umlatt and Spink that episode.
Perry "Coma" is an old, old joke about real Italian-American singer Perry Como, whose voice and singing style were so smooth and/or boring, it would put you in a coma.
Here's an early, 1947 use from NBC Chimes, an NBC radio newsletter.
"Perry Coma" was also used as a moniker by a KPTF radio DJ from about 1981-1983.