I know a song that'll get on your nerves

We've all had it. We've listened to a catchy song, but once the song has stopped playing, it keeps on going in our heads. We have a song stuck in our heads. Luckily, unlike having physical objects stuck in our heads, this phenomenon is harmless, but is more likely to irritate women than men.

What I want to know, which is the worst song for getting stuck in your head? My brother introduced me to the amazing 'Banana Phone' song.

Of course there are other songs which seem to make their way into your brain. One of my favourites is Total Eclipse of the Heart by the gravelly-voiced Bonnie Tyler.*

In German, they call this phenomenon Ohrwurm or earworm. But unlike real parasitic worms, this is just a metaphor.

So, quick questions:

1. What makes a song get stuck in your head?
2. What's the most annoying song you know?
3. When was the last time you had a song stuck in your head, and how long did it last for?

*Bonnie Tyler's famous raspy voice comes from an operation she had to remove nodules on her vocal chords. She was ordered not to speak for several weeks after the operation, but did so, giving her voice its unique quality.