Ok. I'll rehash this old chestnut.

Little boy goes into frozen food shop and says to the man "My mum says can I have a packet of Birdseye Pissoles please. "

Man frowns, then smiles and says "Ah, of course, little boy, but next time try to remember that it's an R, not a P!"

"OK," says the boy, "My mum says can I have a packet of Birdseye Arseholes please."