I saw him on a stand-up show one time, years ago, doing the old "no, I said 'posse'!" cowboy joke (look it up), with a lot of these guys playing the characters in the joke (DeNiro, Williams, Pacino, etc.), switching back and forth, rapid-fire between the characters (Phil Hendrie x20, but with the physical/visual changes too, not just the voices!).
I was floored.
He was doing DeNiro as the lead cowboy part, talking to his horse (after his horse had messed up in bringing help...again, you can find the joke online I'm sure). Anyway, he's standing there, smacking the "horse" in the face, riffing on the bit from "Goodfellas", saying "What did I tell you? What did I tell you? *smack* What did I tell you?" (where DeNiro is berating the guy from showing up with the flashy pink Caddy after their airport heist).
It was dead-on and so hilarious because he had the DeNiro face and voice going, but with a silly-looking 10-gallon hat on, smacking this toy stick pony prop, with full-tilt "DeNiro menace" engaged.
The audience, I remember, was going nuts because it was so damn well done.