A few days back, I was in a store shopping. The store's music selection changed to Pharrell Williams' song "Happy". Immediately, I softly started singing along, not loud, not consciously exactly. Bopping along with the music. Just couldn't help it. Then I thought - ooops, wonder if anyone heard/saw that and looked around. And wouldn't you know, I saw several other people doing the exact same thing and one woman looked up and we looked at each other and said, "you just can't help it!" It was great. Big smiles and continued... What other songs can you think of that brings on that kind of spontaneous joining in with the song? - in a public place too!