Bert is intelligent though also grumpy, boring, and easily frustrated. He enjoyed such dull activities as bottle cap collecting, pigeon watching, and oatmeal cooking. A typical "Ernie and Bert" skit has Ernie coming up with a hare-brained idea and Bert attempting to talk him out of it, ending with Bert completly losing his temper and Ernie remaining oblivious to his own bad idea. The most famous of such routines was the Banana in my ear sketch.
Ernie and Bert share an apartment whose address is 123 Sesame Street. They sleep in separate beds, which has led to the occasional accusation that they are representations of gay lovers.
A website, "Bert Is Evil," hosted digitally manipulated images that depicted the muppet consorting with Adolf Hitler, Osama bin Laden, and the KKK. The owner of the website has since taken it down, but some mirrors still exist.