Wrestlers

The Wrestlers are extremely minor characters that appear in the very first Regular Show episode entitled The Power. They are seen at the start of the episode when Rigby is watching a wrestling match in his room while telling Beef Burrito (a doll) to "take back" what he said about his mom.

Trivia
The main wrestler is the same guy that "Beef Burrito" is a doll of, so he is probably Rigby's favourite professioanl wrestler.