A favourite earworm of yours truly!
The above is a studio recording (for Decca?). Following is the song from the film soundtrack, same artists (I think Victor Young conducts):
‘Busy Doing Nothing’ (music by Jimmy Van Heusen) from the film A Connecticut Yankee in King Arthur’s Court (directed by Tay Garnett; released 1949) sung by Bing Crosby, William Bendix & Cedric Hardwicke.
who wrote the lyrics?