Pootworm
The Pootworm is a worm that the Pkunk use to prove The Captain that he is alive, when they first greet him in space. Specifically, they say:
"Welcome to our home stars. We are the Pkunk. Pkunk we are. Seekers of the deepest truths, askers of interesting and significant questions. Even now a question of great transcendental significance comes unbidden to our minds. Who are you and what do you want? Do not be frightened. We are powerful creatures, yes, but we could not hurt you anymore than we could squish the helpless Pootworm. We love the Pootworm. We are one with the Pootworm. We are one with you. Of course you realize that this means you are one with the Pootworm. Rejoice!! To be one with the Pootworm is to be alive, and why not be alive? Is that not what living is for?"