From Rocklopedia Fakebandica
Wapsi Square (2001). The band—Jacqueline Bontemps (drums), Owen Albrecht (guitars/keyboards), Shelly Wahnee (bass)— took their name from an incident early in the strip, when another character (Monica) attempted to brush her teeth in the dark. Instead of toothpaste, she squeezed the contents of a fermented banana onto her toothbrush. Yeah, we're not buying the whole concept of a person keeping a fermented banana next to the sink either. Name origin strips here and here.