Last night, Jimmy Kimmel would not be denied the spotlight, even though he knew, you knew, I knew, we all knew that everyone would be tuning into Conan O'Brien to see what he'd do on The Tonight Show. So. What to do? How about putting on a fake wig and chin and doing the entire show as Jay Leno? No. Seriously? That's what Kimmel did. It was amazingly weird, for all of the reasons you're guessing, but even more so considering that one of his guests was Chevy Chase, who not only works on an NBC show currently but also more infamously had one of the more infamously brief appearances of his own in late-night TV. Which probably explains why Chase dressed up as Conan but for some reason tried to duplicate Kimmel's Leno accent. That's what his lisp was about, right? I don't know. Just watch the clip.