This is ChickenBoo, the idea came from Animaniacs. In the show, the character can't be seen for what it really is as long as it has a disguise on, it always looses it's disguise during the show and gets exposed for what it really is, a giant chicken.
Is Bruce a chicken in disguise? We might not ever know.
Here is a chicken-boo episode, they are always short, sub 5 min although this one is 3 : https://www.youtube.com/watch?v=Ez1IgYWkzs8