William Wimperson is a character who appears in "The Bad Guy". He is shocked like the rest of the Doomstone resident at Wander calling them "wimpy wimpersons".
William, for whatever reason, corrected him by saying that his name was spelled "William Wimperson". He's not seen with the rest of the baddies when they corner Wander and Sylvia, but it can be presumed that he admitted to being a faker at some point between that and their leaving.
He looks like a living cactus, with a hat matching his look. He also has a red handkerchief, and a few holes on his body.