In 2006 the definition of a planet changed, resulting in Pluto being reclassified as a dwarf planet. "Poor Little Pluto" takes a tongue-in-cheek look at the issue and declares, "You're still a planet in my heart." Though it's not a particularly scientific song, it does make a great cross-curricular tie-in to study of the solar system.
The song is mostly unison, but the optional Part 2 makes the tune a call and response in the second ending. (from Music K-8, Vol. 17, No. 5)