Which celebrity guest on the podcast has vibed with the show the least?

I'm sure this question has been asked before, but I'm wondering which A-block guests have just not vibed with the show and been put off by the characters. One I remember from way back was Jane Lynch who did not seem to be having a good time. But who have been the worst celebrity guests who just didn't seem happy about the improv and just didn't fit into the overall energy of the podcast?