I saw him in concert at SU. It was the "Dirty Work" tour, in conjunction with the release of the movie.
Anyway, he was 15-20 minutes late coming out on stage. He apologized and said he was having stomach issues. He spent at least the first half of the concert talking about his stomach, diarrhea, asking members of the audience if they've ever had stomach issues like this, about their worst bouts of diarrhea...It was hilarious.
A month or so later, one of my classmates came back from visiting her boyfriend at the University of Michigan. She said Norm Macdonald was in town and they went to the concert. And she said it was kind of a strange performance, because he came out on stage 20 minutes late, and then he went on and on about some stomach issues he was having...