When he couldn't hold it together after Kristen Stewart and Robert Pattinson broke up.
When he had a drum-off with Chad Smith of the Red Hot Chili Peppers.
When he performed as Robert Goulet, while continuing to confuse Conan for Johnny Carson.
When he came on as Ron Burgundy and shared his tips on how to survive a prison riot.
When his Olympic patriotism led to an impromptu U-S-A chant among the audience.
When he sang his own special version of "Danny Boy" in honor of St. Patrick's Day.