I did! And I was laughing so hard I started crying when he made the little curl of hair on his forehead. (I should note, for those who go to watch the clip, that you're coming into it cold. He was in fine form, mugging for the camera for a good ten minutes before he did the Superman bit - it was funnier, perhaps, when you build to it.)
You should be able to see it here:
Stephen Colbert While the commercial plays, go to the side and select "Daily Show - Colbert", then "Fresh Stephen" and you'll find it in the "Threatdown - Science" clip.