Space Killer is a former game at Super Silly Fun Land. Appearing to be rigged, it is operated by a carnival barker who is only interested in taking people's money. The booth is mostly destroyed by Felonius Gru with his big blaster cannon.
The player, using a gun that shoots small balls, has to shoot and knock down a UFO target to win a prize. The prizes include a big stuffed unicorn and other soft toys.
Agnes, seeing the large unicorn prize at the Space Killer game booth, begs Gru to let her and her sisters play. Margo, Edith, and Agnes attempted to play twice. The second time, Agnes strikes the target.
The carnival barker refused to give her a prize because the UFO is supposed to be knocked down. Gru, angry, "knocks down" the target by nearly frying the Space Killer booth with a fireball gun. Agnes's prize is surrendered, and Gru, possibly for the first time in years, is praised in a way that touches his heart, which would mark the start of his reformation.