Now this isn't the song you're after, but this thread brought it to mind

"My Name is David Trimble, I'm nifty neat and nimble,
On my backside there is a pimple and it festers in July
I try so hard to please it, with ointment I do grease it,
But the only way to ease it is to go marching with the boys.
Chorus
It's a little orange pimple, so soft and cute and simple.
As harmless as a dimple till the marching season comes
Then it swells with indignation, it causes irritation,
How can I sit in negotiation with a pimple on my bum?

There are lots more verses, and they are in the Frank Harte trubute book "A Living Voice" (the song is by Sean Mone)