A fellow took his parrot on its perch to the folk club and proudly boasted that if you pulled the bird's right leg it would sing "A Childe Ballad" from beginning to end. If you pulled its left leg it would sing "The Death of Nelson"

Sure enough the parrot did exactly that!

Then some smart-arse in the audience said what happens if you pulled both of its legs at the same time?

The parrot quickly replied "I'd fall off my perch, you idiot".