It was an incredible comedic performance. (By his co-stars too, btw, but he carried a lot of the film, I felt.). Also an overall very funny movie.

I'm not sure exactly how much of Graham Norton is scripted, but he's had at least a couple of amazing appearances on that. (It's a bit of an edge case, but I'd argue that it qualifies as 'acting' even if only slightly so.)

EDIT: I gained a lot of respect for him -- as an actor -- after NG. I'm told comedy is one of those things that it's really hard to do well.