a humbug - A tiny, annoying insect that crawls up your butt while you s

A tiny, annoying insect that crawls up your butt while you sleep and hums bad songs.

I woke up with a humbug on my butt. It was singing 'Never Gonna Give You Up.'

My brother said he got a humbug. He screamed and jumped out of bed.

I had a humbug crawling up my leg, and it was singing my favorite song backwards.