I think earworms are very personal. When I was in HS, there was a Tears For Fears song that always got stuck in my head. Now, with flick of a memory switch - I can get it stuck again... "everybody wants to rule the world" (crap...why did I do that??)

Singing 'Somewhere Over the Rainbow' will unstick just about anything for me (without getting stuck itself).

And, is not 'Small World' the worst earworn offender of all time??