During the Who's Carl This Time? round, Peter confused St. Peter with St. Paul, causing P.J. to correct Peter. This lead to Luke and Paula to join into the fun.
Peter had a verbal trip up when introducing the Bluff the Listener game to the listener contestant with "what is, means... that" rather than "what this means is that". Paula called Adam Riess a physicist, in which Adam clarified that he was an astro-physicist and jokingly taking offense to that.
Listener contestant in the Listener Limerick Challenge round actually said "wait, wait... don't tell me" when trying to come up with an answer.