Steve has had several unpleasant experiences involving turnips. The turnips, complete with arms, legs, and faces, will go to great lengths (including the use of chloroform, like in Comic 43) to be eaten by Steve.
It all started when Steve met Timmy the Turnip in Comic 32, who purportedly was rich in vitamins and minerals. When Steve refused to eat him, Timmy subdued him and forced his way into Steve's mouth.
He later attempted to take advantages of Steve's temporary zombification by disguising himself as a brain in Comic 110, but failed.