Songwriter Alex Call came up with it while sitting under a plum tree. He told Songfacts the story: "Despite all the mythology to the contrary, I actually just came up with the 'Jenny,' and the telephone number and the music and all that just sitting in my backyard. There was no Jenny. I don't know where the number came from, I was just trying to write a 4-chord rock song and it just kind of came out.

This was back in 1981 when I wrote it, and I had at the time a little squirrel-powered 4-track in this industrial yard in California, and I went up there and made a tape of it. I had the guitar lick, I had the name and number, but I didn't know what the song was about. This buddy of mine, Jim Keller, who's the co-writer, was the lead guitar player in Tommy Tutone. He stopped by that afternoon and he said, 'Al, it's a girl's number on a bathroom wall,' and we had a good laugh. I said, 'That's exactly right, that's exactly what it is.'