Question: Al Jolson who stared in a 1927 "talkie" was once dubbed what?

Context paragraphs:
The Jazz Singer (1952 film): The Jazz Singer is a 1952 remake of the famous 1927 talking picture "The Jazz Singer".  It starred Danny Thomas, Peggy Lee and Eduard Franz, and was nominated for an Oscar for best musical score.  The film follows about the same storyline as the version starring Al Jolson.  It was also distributed by Warner Bros.  Pictures.

Irving Cohen: Irving Cohen was a character that Martin Short used on "SCTV", and brought with him to "SNL".  Known for his admiration of Al Jolson, Cohen was a caricature of old Tin Pan Alley songsmiths, and the running gag in any sketch where he appeared was that he would claim that he could "write a song about anyt'ing," at which point Irving would call to a pianist off camera, "Give me a 'C', a bouncy, 'C'", and then he would ad-lib lyrics, ending with, "Da-da-da-da-dee, da-da-da-da-dah, ah, whatever da hell else ya wanna put in da t'ing!"  This off camera pianist seemed to follow Cohen everywhere, even bursting into song in the middle of a HUAC hearing.  Cohen started his interviews by reminiscing about the old days, starting off with, "In the old days, we had a t'ing, called, 'Vau-de-ville'..." He also frequently name-dropped Al Jolson and Sophie Tucker and had a habit of punctuating sentences with the phrase "at this time."

The Jolson Story: The Jolson Story is a 1946 Technicolor musical biography which purports to tell the life story of singer Al Jolson.  It stars Larry Parks as Jolson, Evelyn Keyes as Julie Benson (approximating Jolson's wife, Ruby Keeler), William Demarest as his manager, Ludwig Donath and Tamara Shayne as his parents, and Scotty Beckett as the young Jolson.

Avalon (Al Jolson song): "Avalon" is a 1920 popular song written by Al Jolson, Buddy DeSylva and Vincent Rose referencing Avalon, California.  It was introduced by Jolson and interpolated in the musicals "Sinbad" and "Bombo."  Jolson's recording rose to number two on the charts in 1921.  The song was possibly written by Rose, but Jolson's popularity as a performer allowed him to claim composer co-credit.  Originally, only Rose and Jolson were credited, and DeSylva's name was added later.

Back in Your Own Backyard: "Back in Your Own Backyard" is a popular song.  Officially the credits show it as written by Al Jolson, Billy Rose, and Dave Dreyer; in fact, Billy Rose was exclusively a lyricist (see ), Dreyer a composer, and Al Jolson a performer who was often given credits so he could earn some more money, so the actual apportionment of the credits would be likely to be music by Dreyer, lyrics by Rose, and possibly some small contribution by Jolson.

Mammy (film): Mammy (1930) is an American pre-Code musical drama film with Technicolor sequences, released by Warner Bros. The film starred Al Jolson and was a follow-up to his previous film, "Say It with Songs" (1929).  "Mammy" became Al Jolson's fourth feature, following earlier screen efforts as "The Jazz Singer" (1927), "The Singing Fool" (1928) and "Say It with Songs" (1929).  The movie relives Jolson's early years as a minstrel man.  The songs were written by Irving Berlin, who is also credited with the original story titled "Mr. Bones".

'N Everything: "'N Everything" is an Al Jolson song by songwriters B.G. "Buddy" DeSylva and Gus Kahn.  Jolson recorded '"N' Everything" in 1917 and then interpolated the song into Sinbad at New York's Winter Garden Theatre in 1918.  Jolson adapted the song with improvisation as performances of Sinbad progressed, leading Jolson to eventually be given co-lyricist credit on the song.  The success of "N' Everything" prompted Jolson to ask DeSylva for further songs.

Me and My Shadow: "Me and My Shadow" is a 1927 popular song.  Officially the credits show it as written by Al Jolson, Billy Rose, and Dave Dreyer; in fact, Billy Rose was exclusively a lyricist, Dreyer a composer, and Al Jolson a performer who was often given credits so he could earn more money.  The actual apportionment of the credits would be likely to be music by Dreyer, lyrics by Rose, and possibly some small contribution by Jolson.

There's a Rainbow 'Round My Shoulder: "There's a Rainbow 'Round My Shoulder" is a 1928 song sung by Al Jolson in the early Warner Bros. talking picture "The Singing Fool" the same year.  The song along with "Sonny Boy" and "I'm Sitting on Top of the World", which was also in "The Singing Fool" became big hits.  The song was written by Al Jolson, Billy Rose and Dave Dreyer.

Al Jolson: Al Jolson (born Asa Yoelson; May 26, 1886 – October 23, 1950) was an American singer, film actor, and comedian.  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."  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."

Supporting paragraphs: The Jazz Singer (1952 film) Al Jolson
Answer: "The World's Greatest Entertainer."