As for the stooges (not a fan), you are thinking of "Shemp."

Sham is usually defined as fake or false. In particular, it gets used in instances where someone is purposely trying to fool someone else, and is used in a negative way. Sham trial comes to mind, sham marriage to help someone get a green card, or to fool others into thinking they are straight when they are gay.

Why did you ask? A bet? Some guy frustrate you by being clueless about a pillow sham or something?

Sham-poo is something you buy at a novelty store, and place on your hosts rug during a drunken party.