Question: What American singer, film actor and comedian, suddenly stood up during a performance of Gershwin's Liza (All the Clouds'll Roll Away) and started singing?  
Sentence (from "Liza (All the Clouds'll Roll Away)"): "Liza (All the Clouds'll Roll Away)" is a song composed by George Gershwin with lyrics by Ira Gershwin and Gus Kahn.
Relevant evidence: Yes