Men in Black 3

In 2012, alien criminal Boris the Animal, the last Boglodite, escapes from a maximum-security prison on the Moon to take revenge on Agent K, who shot off his left arm and captured him in 1969. He confronts K and his partner Agent J, telling the former he is “already dead”. K attempts to prevent J from pursuing Boris and refuses to give any exact details about the events of his arrest. Back at MiB Headquarters, J discovers K was responsible for not only capturing Boris but for deploying the “ArcNet”, an interplanetary shield that prevented the now extinct Boglodites from invading Earth, but is denied any other details about the case.

Boris travels back in time to July 16, 1969, to kill K’s younger self, altering history. With only J’s memory somehow unaffected, no one else at the Agency understands his knowledge regarding K until Agent O, the Chief of MiB following Zed’s death, eventually pieces together J’s erratic actions (such as craving chocolate milk) as signs of a fracture in the space-time continuum. With K gone, the ArcNet was never deployed, and present-day Earth is defenseless from a Boglodite invasion.