The song was covered among others by Rudy Vallee, Billie Holiday, Jimmy Durante, Louis Armstrong, Frank Sinatra, Nancy Sinatra, Natalie Cole, Harry Nilsson, Carly Simon, Vera Lynn, Bob Dylan and Bryan Ferry.

The song was reintroduced in the 1942 film Casablanca, where it was sung by Sam, portrayed by Dooley Wilson.

Sam's piano accompaniment was played by a studio pianist, Jean Vincent Plummer; Wilson was a drummer.

[9] Wilson was unable to make a commercial recording of the song at the time due to the 1942–44 musicians' strike.

A plaque on the second floor of the Valley Regency Catering Facility in Clifton, New Jersey, commemorates the song.

Yet, we get a trifle weary with Mister Einsten’s theory, So we must get down to earth, at times relax, relieve the tension.