Like Krusty, he is a heavy smoker, and often seems depressed off-stage. He was once seen playing Wii Sports with Krusty. He is sometimes seen as Krusty’s driver, accountant, and butler. He's a classic act in Krusty´s show when he does "monkey business". Mr. Teeny also rescues Krusty from a bomb carried by a brainwashed Bart.
Mr. Teeny is originally from Brazil. His uncle was once the head monkey at the Bureau of Tourism in Brazil and his mother's name is Toot-Toot, and she calls him Louis when they're reunited.
Also, it's revealed there have been other monkeys that went by the name "Mr. Teeny," and that the current one and the very first Mr. Teeny couldn't hold a candle to the third Mr. Teeny (Krusty admitted the second Mr. Teeny was okay since he helped Krusty pick up women).  Krusty once called the current Mr. Teeny in his possession Mr. Teeny Number Seven.
Teeny was a writer for the “Good Guy Awards” and quit after being insulted on-stage by Krusty.
He is an immigrant from Brazil and was deported when Krusty went broke, but has since returned. In "Coming to Homerica" while playing chess with Mr. Teeney, Krusty said that "you fell for my trap just like in Africa" hinting he was born in (or at least lived in) Africa. Since there has been more than one Mr. Teeny some of them may have come from Africa while others came from South America.
He wears a pink hat and bow tie, but has also been seen in a tuxedo and gold encrusted thong.
Krusty has implied that if he can't find a human willing to donate a lung when he gets cancer, he's planning on harvesting one from Mr. Teeny.