My 5-year-old *loves* to sing, and she has these really inventive songs that she'll do. She actually has a bit of a tune to it, and she'll tell a whole story. Like, she'll summarize the entire gospel in a song. It's hilariously cute. She never seems to do it when I have the camera ready, too.
I saw one of those videos where they have kids tell a story and then the dads act it out, and it was the Bible story about the rich man who was in debt to the king, and the poor man who was in debt to the rich man. When the rich man is trying to convince the king to forgive his debt, he asks him to "let it go"... which then causes the kids to both break into song, singing "Let it go!" It's so funny. Apparently the singing convinces the king to be lenient. So then the rich man goes to the poor man and asks him to pay him back, and the poor man (voiced by a very young boy) tries to sing "Let it go!" too... and he says, "Uh... I don't know any more words," and the rich man doesn't forgive him. It's hilarious.