Bert is a Muppet from Sesame Street with a somewhat grumpy disposition. He can be considered to be the predecessor to characters such as Squidward and other similar cartoon characters. He is constantly annoyed by his brother Ernie.
According to popular Internet lore, Bert is not merely a crankcase, but actually evil - evidently, he is a close friend of Osama bin Laden, and to a lesser extent, other bad guys.
Bert represents Terror Alert Level Yellow