Beginning, Middle, and End are three Anything Muppets that Betty Lou uses to demonstrate those three words. They appeared in a season 2 segment. (First: Episode 0138) Beginning, Middle, and End are respectively made from Reddish-Magenta, Green, and Purple Anything Muppet patterns.
At first she only talks with Beginning and End, who attempt to tell a story, but without a middle their story ends up becoming very dull. Ater getting Middle to join them, the story becomes much more interesting... too interesting, as Middle can't stop reciting the story. End must cut him off, and the three end up quarreling with each other.