Stop with the Kicking, he did a routine about the Star Trek movies. It's pretty dated, back when impressions of Christopher Lloyd and Dudley Moore were cutting-edge, but it's still funny. The thing to watch is his William Shatner. It may not be the most accurate in terms of the voice, but Pollak's is (I think) the funniest in terms of capturing Shatner's weird cadence and gestures. The word "personalities" has never been funnier.
Oh, and if you're wondering about the ending, that's supposed to be Brian Boitano. Callback to an earlier routine Pollak did. Doesn't get any funnier in context, though.
If you're wondering what Shatner himself thinks of Pollak's impression, check out this video.
UPDATE: Corrected the spelling of Pollak, added bonus video.