Uncle Harvey is the fictitious name Sheldon gave their tank of liquid helium that was purchased illegally from a contact that Howard knew. Sheldon dressed him up in a hat, scarf and coat and even tipped the hat when they passed somebody in the hallway. The tank appeared in "The Helium Insufficiency".
- Jim Parsons did the play "Harvey" on Broadway in New York City in summer 2012, which is about a invisible white rabbit. His Uncle Harvey also didn't exist.