Thanks to Keboroxu for correcting me on a dog's preference, so . . .

Fluffy's song

Raindrops on roses, and snacking on squirrel.
Guarding the door against that nasty Quirrell.
Hearing how Hagrid can hatch dragons' eggs.
Taking a bite out of Master Snape's legs.

Listening to music that can get me sleeping.
Dozing, ignoring the trapdoor I'm keeping.
Letting three kids past, now that's rather bad.
One was that 'Potter' he's quite Jack-the lad.

Now I'm harassed, and embarrassed, and I hope you see,
Despite inattention, to ingress prevention
My other heads won't agree.