From Muppet Wiki

Sinister Sam is a mean-looking cowboy who appears in several Old West sketches on Sesame Street. Like Bad Bart, it seems like he's going to make trouble, but he turns out to be harmless.

Sketches

• The Biggest Man (EKA: Episode 0704)

Sam is looking for the biggest man in the place because he has a big cowboy hat for him.

• Doc Holiday

Sam runs to the saloon to find Doc Holiday, because of his itchy trigger finger.

• Box of Crayons

Sam announces that someone has bought the last box of crayons, and he wants to know "why." It turns out that he just wants a crayon so he can learn how to write the letter Y.