Worst ear worm I ever had wasn't musical. It was numeric. It was the firing order of a Chevy small block. 18436572. Over and over and over. That motor ran in my head for three days before it ran outta gas.
I once decided to splurge for a Chevy dealer tune-up on my Chevy Caprice wagon with a 305 cid engine; it was time and I was too busy at work to do it myself. They got the firing order wrong. . One of the many reasons I'm no longer a GM fan.