Hobo Bob is a book-exclusive character who only appears in Chapter 5 of Wayside School is Falling Down. Sharie brings him in for Show-and-Tell one day, and the rest of the class asks him questions in his only appearance.
He is described as having a large jacket which is too big for him, but not as large as Sharie's jacket. He also wears pants with many colourful patches on them. He wears shoes which also are described as looking too large, but this may be due to the fact he doesn't wear socks. He also has a long, scraggly beard and long hair as well.
Hobo Bob's character carries a strong disliking of socks. When he was young, Bob won a spelling bee without wearing socks, and ever since have thought of socks as being unlucky. The other students at Wayside School seem to take the advice close at heart, and take off their socks right before a spelling test. He also is very generous towards children, to an extent where he will not even take Sharie's quarter. He is also seen answering the questions of various other students in his only appearance, who question him about various aspects of his life. He reveals facts like how that since he didn't grow up to become anything in his life, he simply became a hobo, he uses the rain to shower (which Myron is jealous of, since he has to go inside when it rains), and only eats Mulligan stew.