Pea Pods (or rather the Pea Pod, as only one is found in the entire game, in Apple Acres) are large green banana-like creatures that get about on two propeller-like legs. It moves quickly, following Keen to some extent and ejecting Pea Brains — between two and seven per Pod. It is harmless, but its offspring are not.
Interestingly, it is also the only creature in the Keeniverse that creates other living creatures (or technically the same creatures, as Pea Brains are young Pea Pods).
The in-game help states of Pea Pods: