Five-man group The Warp Zone performs one of the catchiest cartoon intro themes from the 90s with impressive timing and coordination. If not the catchiest, although there were so many good ones, it's really hard to pick a number one.
One man. 21 video game theme songs. A whole lot of really, really silly costumes.
This is an A Capella version of Cara Mia, the "turret opera" from late in Portal 2. I don't really know why you'd sing this, but vocalizing music as beeps and boops is a big part of A Capella, so it works just fine.
Danny Fong applies his amazing vocal talents to the Pokémon television show theme song, performing not only all the voices, but vocalizing the music as well in a stunning display of a capella coordination and shirt variety.