I don't write songs, but here are some of my favorite songs about surprising subjects:

I SHOT YOUR DOG by Fred Eaglesmith.

BRANCHING OUT by John Gorka. "When I grow up I want to be a tree."

SWIMMING SONG by Loudon Wainwright III.

NaCl (SODIUM CHLORIDE) by Kate McGarrigle.

GALAXY SONG by Eric Idle and John Du Prez.