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.
- Sam runs to the saloon to find Doc Holiday, because of his itchy trigger finger.
- Sam is looking for the biggest man in the place because he has a big cowboy hat for him.
- 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 draw the letter Y.