Unfortunately, Keef causes trouble for Zim when he wants to bring the rest of the rejects to his home. Out of fear of being discovered and anger at Keef, Zim ultimately has to convince Keef that a squirrel outside is his best friend with the aid of robotic eyes he implanted in his head. After being attacked by the squirrel, Keef disappears. However, he does not die. Keef remains in the background at Skool, keeping a distance from his former best friend. They make no contact with each other for the rest of the series.
However, had the series continued, the episode "Return of Keef" would have revealed that Keef is still preoccupied with their withered friendship. Thinking that Dib and Zim are friends, he makes another mess of things when Dib goes along for the ride. In the end, Zim and Dib have to team up in order to finally get rid of the redheaded nuisance. He ends up exploding from joy after seeing Dib and Zim hug, but because of network request, Keef (of course) does not die, and resumes his role as a background character.
In this episode, Zim attempts to befriend someone in the hopes that it will make him appear more human. He immediately goes over to the "reject" table, filled with children who evidently have no friends. Keef is one of the children who sits at this table. Putting together a contest to see which one of the children will suffice, Zim ultimately picks Keef as the winner. Their friendship is sadly one-sided and lasts merely for the rest of the day. Upon reaching Zim's house after school, Keef is told that he has played the part of a friend rather well, but that his "services" are no longer required. Zim is initially victorious, but is hesitant when he realizes that Keef has not taken the hint and continues to stalk him relentlessly.