Here's a good one. Remember the early GEICO Gecko ad where he tries out to be in a GEICO commercial?
Then, the Taco Bell Dog comes out of the interview.
"Oh great, a talking Gecko!"
Well, halfway through the ad, look who's sitting next to the Gecko!
It's Saturday Night Live's Fred Armisen
I can't PROVE this one...it's nowhere online. But damned if I'm not pretty sure! It's even more obvious in the moving video than it is in this still photo.