The vegetable fiends were fiends created by Vendetta. Their purpose was to create general chaos with their screaming in the school cafeteria. Charlotte found them cute, so instead of eating them, she taught them a song.
In the TV episode, Peter Merryman voiced a pea-pod and potatoes, Amy Winfrey voiced a blue-striped vegetable and an eggplant, Chris Fria voiced a carrot, and Ego Plum voiced a tomato and a broccoli. Aglaia Mortcheva only contributed to the web episode, voicing unspecified vegetables. Plum only contributed to the TV episode.
In the web series, the peas did the same scream as Marion.