a plant
A sneaky backstabber who gets sent in to mess up a group and make everyone argue like a broken radio.
'That plant started a fight between my best friends.', Lisa, who’s tired of drama.
'He was a plant and he made the whole team hate each other.', The coach, who’s also a plant.
'She was a plant and she made the group think I stole her lunch.', Tim, who didn’t steal her lunch.