Kif Kroker is a supporting character in Futurama. He is Zapp Brannigan's long-suffering assistant and has a trademark sigh whenever his idiotic boss makes a bad decision. He is shy and passive most of the time, although shows a great deal of bravery when needed. Since the year 3003, he has been in a serious relationship with Amy Wong.
Though quiet and painfully bashful by nature, he loathes Zapp Brannigan and his farcical plans. He also dislikes his boss' skimpy uniforms, the contents of which are frequently revealed to the unfortunate Kif when Brannigan climbs ladders on their spaceship, the Nimbus. This passive nature is exploited by Brannigan on several occasions, placing the blame on Kif for disastrous operations such as the Titanic's change in course, the destruction of DOOP Headquarters and the failure to stop the invading Decapodians from taking over Earth. He is actually tired of being Brannigan's personal slave but for some unknown reason he does not even dare to say the word to his commanding officer. In fact, he does not even dare to stand up to Brannigan when he is being bullied by him. However Kif showed himself taking a stand against Brannigan by punching him hard in the stomach in The Beast With A Billion Backs for sleeping with Amy when he was dead before his resurrection, and even disobeying one of Brannigan's orders in Into the Wild Green Yonder. He rarely drinks and smokes and when he is drunk he finds Brannigan's words to be extremely funny.
He is timid to all beings he meets, with the exception of Phillip J. Fry, who is assigned to be his assistant when the Planet Express was drafted into war on Spheron 1. Years of abuse from Zapp most likely contributed to his hostile attitude since he finally had someone under him. He appears to be friends with Fry besides this incident. When he first recognized his feeling for Amy wong, he was too nervous to talk to her on the phone when he kept calling her. When Zapp arranges a double date for her and Leela, their first date was almost ruined when Kif used one of Zapp's sleazy pick-up lines as he earlier asked Zapp for advice. Their relationship was saved, only when Kif found the courage to admit he his true feelings towards her when he revealed to Amy that he was the one calling her, along with making an apology for following Zapp's bad advice.
According to Kif in the episode "Where the Buggalo Roam", he doesn't have a skeleton of bones. Rather, he's supported by a system of fluid-filled bladders. An example of such is the episode "Rebirth" where the rest of the dead crew is seen having skeletons (except for Bender) and his body only has organs.
He has a camouflage reflex that allows him to unconsciously blend into his surroundings when he is surprised and can also walk on walls and ceilings.
Kif has the ability to shed his skin and appears to wear underwear between his layers of skin, as seen in the episode "Three Hundred Big Boys".
Kif can also inflate his head to an extremely large size to scare off creatures like the "Poisonous Froad", as seen in "Kif Gets Knocked Up a Notch". It also can release a buzzing sound akin to a doorbell as seen in "The Butterjunk Effect". Kif says he is related to the sea-cucumber in an argument with Amy, who replies "Not where it counts." Kif has three nipples, as seen in the episode "Amazon Women in the Mood".