The experience of getting a song stuck in your head is somehow universal. A casual association reminds you of the beat or the melody or the lyrics and before you can say "Supercalifragilisticexpialidocious" the song had taken up residence and you will be living with it for the next two or three eternities. The squatter in your brain can range from benign to maddening. Occasionally they will leave their own, but usually they have to be forcibly evicted by (per the usual method) trying to invite a more tenacious guest supplant them. The most disconcerting for me is when someone around me starts singing along, in sync with the song my head. Then I know that the invading troops have suborned my vocal cords and are launching a sotto vocce invasion of the world around me.
But the point is that it isn't only songs that get stuck on mental flypaper. While earworms are the most common, I've discovered that many people experience the equivalent with their own unique mental constructs. For one of my sisters, it is typing sequences on a keyboard. One of my friends has numbers follow him around. In my case it is words.
Words that get stuck and repeat themselves in my mind for hours or days at a time are necessarily interesting. (Or at least, I only ever notice one that is uncommon.) The ones that stay the longest are those whose meaning or usage have somehow escaped me. The less I know about the word, the more insistently it presents itself, as though it is confident that this time, there must surely be a way to apply it to the situation. In these cases looking up the definition is often enough to start the eviction process.
Anyway, here are some examples of my recent thought-guests. I will post more as they come up, with far less of an introduction.
EDIT: It looks like I've mentioned this in passing before.