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?  

"Liza (All the Clouds'll Roll Away)" is a song composed by George Gershwin with lyrics by Ira Gershwin and Gus Kahn.  It was introduced in 1929 by Ruby Keeler (as Dixie Dugan) in Florenz Ziegfeld's musical "Show Girl".  The stage performances were accompanied by the Duke Ellington Orchestra.  On the show's opening night in Boston on June 25, 1929, Keeler's husband and popular singer Al Jolson suddenly stood up from his seat in the third row and sang a chorus of the song, much to the surprise of the audience and Gershwin himself.  Jolson recorded the song a few days later on July 6, 1929, and his rendition rose to number nine on the charts of the day. <SEP> Davy Knowles (born 30 of April 1987) is a Manx blues guitarist and singer.  Knowles currently tours as a solo artist, but is formerly of the blues-rock band Back Door Slam, as well as working under the name Davy Knowles and Back Door Slam for a short period of time.  With Back Door Slam, he played lead guitar and sang on their debut album, "Roll Away".  After a split-up with bassist Adam Jones and drummer Ross Doyle, Knowles released the first and only album under the name Davy Knowles and Back Door Slam, "Coming Up for Air", on 19 May 2009.  Knowles drew his musical influences from blues musicians that he grew up listening to such as Dire Straits, Peter Green, and Eric Clapton's Cream.  Due to his home country's proximity to Ireland, Knowles has stated that his music also is influenced by the Celtic genre, which is noted to be present in the song "Roll Away".  In April 2009, Knowles toured with British guitarist Jeff Beck on his American tour, where he was the opening act.  He toured with Joe Satriani and Chickenfoot in the United States through December 2009.  Davy Knowles toured with The Rhythm Devils in 2010. <SEP> Kyle John Echarri (born June 20, 2003) is a Filipino-American singer, recording artist, and actor.  He was born in Orange County, California and started singing at the age of two.  His family moved to Cebu City, Philippines in June 2014.  Echarri rose to prominence and made his first television appearance at the age of eleven when he joined season 2 of "The Voice Kids", where he landed Top 6 under Sarah Geronimo's Team Just six seconds after he started singing One Direction's "Night Changes" during the blind auditions, Coaches Bamboo and Sarah already turned for the then 11-year-old Cebuano footballer eventually choosing to be part of Team Sarah.  A commemorative album was then released by MCA Music featuring Kyle Echarri's performances tracks "Got To Believe In Magic" and "Hero". <SEP>  At the peak of his career, he was dubbed "The World's Greatest Entertainer."  His performing style was brash and extroverted, and he popularized a large number of songs that benefited from his "shamelessly sentimental, melodramatic approach." Al Jolson (born Asa Yoelson; May 26, 1886 – October 23, 1950) was an American singer, film actor, and comedian.  Numerous well-known singers were influenced by his music, including Bing Crosby, David Bowie, Bob Dylan, Rod Stewart and others.  Dylan once referred to him as "somebody whose life I can feel."  Broadway critic Gilbert Seldes compared him to the Greek god Pan, claiming that Jolson represented "the concentration of our national health and gaiety."