Sam and Dean were in a town for a hunt, and they kept breaking out into song. Other people around them would chime in and be back up singers/dancers, but they would never remember what happened. When they were in a diner Dean sings 'The Way We Used To Be' by Daughtry. Later at the laundry mat (I think) Sam realized that he was in love with Dean. He knew that he was going to start singing so he freaked and ran into the bathroom. He started singing 'I Won't Say I'm in Love' from Disney's Hercules. Some random chick bursts out of one of the stalls and becomes one of the muses and sings back up. They later find out that it's because of a Siren.

Any ideas?

Thanks,
Dec