Elvis Costello is a musician.
He had been the musical guest in 1978 where he was supposed to perform his song "Less Than Zero." 30 seconds into the song, Elvis Costello stopped his band stating “I’m sorry, ladies and gentlemen, but there’s no reason to do this song here." He then performed "Radio, Radio", a move which caused him to be banned as he had changed his plans without notifying Lorne Michaels.
However, the ban was eventually lifted and Costello was formally reinstated in 1989 where he was invited back again. Costello even parodied his own stunt on the 25th anniversary show by interrupting the Beastie Boys' performance of "Sabotage" which quickly morphed into a joint performance of "Radio, Radio.". On May 18, 1991, he once again was the musical performer at the time when George Wendt was hosting.