Side Eye is the first boss of the Donkey Kong Adventure mode in Mario + Rabbids Kingdom Battle.
Side Eye is first encountered eating Bad Banana slices and refusing to give them up to the nearby Ziggies. Afterwards, when Donkey Kong and co. arrive, Side Eye takes its weapon from the Ziggies, only to be locked out of its Bad Banana supply. This suddenly causes it to run behind a cover block in fear.
In battle, Side Eye's main attack involves it shooting a bomb from its Bomb Bludgeon at the targeted character for moderate damage. If attacked while not its turn, Side Eye will move away from the heroes.
Upon being defeated, Side Eye will defuse from the item it was merged with: a wooden mallet.