There was a joke a bit like that in the Order of the Stick webcomic.

The hydra they were facing was supposed to be a test of wit. Fighting it mindlessly was supposed to be a bad idea, since it would just grow more and more heads in response.

Except one of them noticed there didn’t seem to be any limit to the number of heads and had an idea, so he let the violent bastard in the team go cut heads like crazy anyway.

After a while the hydra just fainted because it couldn’t supply oxygen to so many brains.