When people sleep, their legs continue to move. This can be easily mistaken for a dream, when really they are suffering from a disease that does not allow them to stop dancing. It is terrible disease because people are not able to get enough sleep. This can lead to deteriorating physical and mental health.
A: I wasn't able to sleep last night because your legs kept moving.
B: Well, I suffer from Restless Leg Syndrome. I cannot keep myself from dancing while I try to sleep. I was doing an Irish Jig last night. That's the worst one.