A senior agent of the Men in Black as well as Agent J's partner and mentor. K has been a member of the MIB for nearly 40 years and is famous for his very serious demeanor.
Born Kevin Brown, Agent K helped found the Men in Black during the 1950's and early 1960's. On March 2, 1961 contact was finally made outside Earth, and it was that event that made K fully devoted to his work. So much in fact, that he left behind a wife to pursue it.
It is in this film that Agent K recruits his future partner Agent J. When we first meet Agent K, he is interrogating an illegal immigrant who he believes to be an alien in disguise. K along with the partner at the time Agent D, unmask the immigrant, who turns out to be a alien by the name of Mikey. At that time a police officer spots the two MIB agents interrogating the alien, and Mikey attacks. Agent D fails to shoot the alien due to his old age, so K quickly draws his weapon and shoots Mikey himself. K then neuralyzes the nearby officers and instructs other MIB agents to burn and dispose of the waste left behind by a dead Mikey. K then takes a seat beside his old partner and listens to D talk about how beautiful the stars are. His partner explains that his spirit is still strong, but his body just can't keep up. Realizing that his partner wants to retire, K puts on the trademark MIB shades and nerualyzes Agent D.
After D retires K learns of a young NYPD officer, and how he chased down a man who turned out to be an alien in disguise. The officer turns out to be one James Darrel Edwards. K is impressed by his effort and admires his refusal to follow orders. K then recruits Edwards to join him in the MIB as his partner. James Darrel Edwards will now and forever be known as Agent J.
During this film K and J have to find and stop an alien cockroach from finding and stealing a galaxy that is located on Earth. If they do not stop him, the enemies of the Roach will destroy Earth to prevent the sub-atomic energy of the galaxy from falling into the wrong hands. The two agents finally encounter the cockroach in the final scene of the movie, where it swallows their guns. K then decides it's a smart idea to be swallowed by this now giant cockroach and retrieve his gun. K tells J not to let the cockroach leave the planet with him inside it, then goes off and dares the Roach to eat him, which he did in one giant gulp. After a long and sort of awkward battle between J and the giant bug, the Roach tries to consume J, but as he tries K then shoots his way out from the inside, killing the alien in the process. K then decides that he wants to retire, so he starts giving the same speech his last partner did about how beautiful the stars are, then requests that J neuralyze him so he can reunite with the woman he loves. Agent J does so, but only after learning that K wasn't training him to be his new partner, but instead his replacement.
In this film K is working as a postal worker in Massachusetts with no recollection of being a member of the Men in Black. Agent J has been assigned with the task of bringing Agent K back to the MIB to help face one of the most feared aliens in all the universe, Serleena. She is searching for the Light of Zartha, which many years ago K had the task of getting the light off of the planet.
When J arrives at the post office K didn't even recognize him due to the fact that he was neuralyzed five years prior. J tries to convince K that he use to be a member of a secret government organization designed to communicate and deal with extraterrestrial life, but without any luck. J then communicates with K's fellow members of the post office who turn out to be aliens. Convinced, K decides to accompany J back to New York City to be denuralyzed. When they arrive back at MIB headquarters they find that it has been taken over by Serleena and they have to go to a pawn shop run by alien Jack Jeebs, who would hopefully help them out by letting them use his homemade denuralyzer. At first it appears that the denuralyzer failed to bring back K's memories, but after walking out and taking a few minuets to himself his memories rush back to him. K bursts back inside and helps J defeat some aliens that attacked him as soon as K left. K still knows some information regarding the Light of Zartha, so him and J follow a series of clues that K left himself 25 years earlier after an alien visit.The clues eventually lead them to locating the Light of Zartha, and they also find them in a fight with Serleena herself. During the fight the two agents manage to save each other, and successfully send the Light of Zartha off into outer space.
In the third installment of the franchise Agent J has to go back in time to 1969 to save a young Agent K from being killed by one Boris the Animal. Boris is an evil alien who escaped from a prison on the moon. In prison Boris came up with an idea to kill K, the man who took off his arm. Boris decided to go back in time and kill K before he was able to arrest him. Boris does just that, which cause Agent K in the year 2012 to vanish and be erased from everybody's mind, except Agent J. J goes searching for answers only to find out from the new Chief Agent O that K died 40 years ago. J gets a hold of a time jumping device and goes back in time to stop Boris the Animal from killing a young Agent K before it's to late.