I've seen mock musicals for a good number of video games, but still I enjoyed this excerpt from Pac-Man The Musical entitled "A Pacapella Song". (Though if I'm being a stickler, it's not technically a cappella, since the song is instrumental musical accompaniment.)
In the song, the ghosts from Pac-Man sing about how excited they are to eat the little yellow guy, and the various ways that they'll prepare him. I'm no Pac-Man lore obsessive, but I always felt a bit like it was Pac-Man who ate the ghosts, but that they simply struck him down with their ectoplasm? Anyway, enough nitpicking, it's a funny song, well performed, and with a predictable yet goofy punch-line. Bonus points for reminding me of the Danny Elfman-penned (and performed!) "Kidnap the Sandy Claws" from The Nightmare Before Christmas.
Props to AJ Pinkerton, who wrote the song, and to the rest of his cast, for giving it their all.