The name of the mission is a portmanteau on "Imp," the zombies that one tries to stop the party for, and "Insomnia," the inability to sleep, making a joke on how one is stopping the loud plant party so that the Imps can sleep in this mission.
The Imps cannot sleep due to the plants having a disco party. Z-Mech 11011-3 makes the player stop the party by destroying all the stereos. When the player destroys the stereos, the player must defeat a Champion Disco Chomper. Afterwards, the mission is complete.
- There are plants such as Weeds and Kernel Corns that will attack you when trying to destroy all the stereos. Vanquish every plant first, then proceed to destroy the stereos.
- Disco Chomper is a legendary variant, though do not let its rarity fool you. It will not activate its ability, since it needs to digest zombies. Thus, staying on a rooftop will make it easy to beat.
The goal is straight forward, and the only classes that gain an advantage are those that can get on top a roof like Foot Soldiers.