Daughter has this song that she sings about Son in the morning. Most mornings. When she wakes up grumpy and cheery sunny Son wants to cuddle and play and interact, she sings this song. I have no idea where it came from, the melody is completely foreign to me so she might have made it up. We try not to make a big deal about it, because she only does it when she's grumpy and we always talk to her about how "being mad at" her brother isn't very nice. And she does play well and love him so so so much of the time.
Anyway, these are the lyrics:
When the sun is up
that's why/when I mad at Finny
When the sun is down
that's why/when I happy at Finny
(she interchanges the why and when often) sometimes she even does motions. both of these videos are pretty hilarious.