Bob is the black-and-white, seemingly disembodied head with large glasses. He usually takes the role of being an avatar to Toxic, and thus frequently appears in animutations made by him.
His origin, according to the official guide to Shumway:
"Like all my videos, this one has that weird looking kid with the big glasses whom I call Bob. I found the picture on some advertisement on the back of an old National Geographic Magazine during a Social Studies class in Grade 8, cut it out and stuck him on the back of my locker on called him Bob. The rest is pretty much history."