The song's writers, Jack Yellen and Milton Ager, had written a number of popular songs, including "Ain't She Sweet
" and "I'm The Last Of The Red Hot Mammas." This one didn't require much effort on their part. Speaking with David Ewen, Jack Yellen explained how "Happy Days Are Here Again" came to be: "In the last week of production, the producer of Chasing Rainbows
phoned me and said he wanted a song for a scene in which a group of World War I soldiers receive news of the armistice. I relayed the message to Ager, whom I hadn't seen in weeks. He said he would stop at my house the next morning, on his way to the golf course. He came in, sat down at the piano, and lighted a cigar. "Got a title?" he asked finally. I didn't have any, but blurted out, "Happy days are here again." The first tune he played was good enough. He kept playing the melody and I scribbled off the first words that came to me and handed him the corny lyrics. His only comment was that he didn't thing the lyric should start with the title. I said I thought it should, and the conversation ended."