Sharing a cookie.
A while back, I said that I couldn't think of a Bert & Ernie sketch in which they were both jerks to each other at the same time. Well, here's one right here: Bert is a jerk for refusing to share his cookie, and Ernie is a jerk for assuming that he's entitled to (at least) half of Bert's cookie.
In spite of that fact, or perhaps because of it, this is a very funny sketch. Bert does some really beautiful physical comedy, and Ernie unleashes his inner Bugs Bunny.