Kimmy is D.J. Tanner's best friend and the Tanners' next door neighbor. While the character was just a recurring guest star early on, she soon became part of the main cast. She was first mentioned in Our Very First Show, but made her official appearance in the episode The First Day of School.
However, it is D.J. who really loves her like a sister. The reason, whether it's because she can live on the edge a little by hanging around her, or because she gets to practice her leadership skills and guide her, is uncertain. It's probably more a desire to help Kimmy, though there is a little of the edge, too. For instance, it's revealed in a later episode that when they were thirteen, Kimmy and D.J. hitchhiked to Berkeley on Halloween. D.J. has also prevented Kimmy from getting way too wild, such as when Kimmy got drunk at a party and D.J. brought her home for the night ("Under the Influence"). Kimmy held a job for a few hours at the brand new movie theater ("Sisters in Crime") and also works at the Smash Club. In one episode Kimmy was about to get married to her long term boyfriend Duane (Scott Menville). She said she wanted to "leave something other than a D average". Jesse and Danny convinced Kimmy not to marry Duane. When Jesse told Duane that they weren't getting married, Duane said his catchphrase, "Whatever".
She is mentioned in the first episode, but we first see her in the third, when D.J. tells Stephanie "Kimmy's not an airhead. She just hates thinking." Kimmy's schoolwork was always average at best, and she copies off D.J. all the time. However, bad grades are only part of the Kimmy Gibbler persona. Her tastes in clothing and other things were quite strange at times. Her parents didn't pay much attention to her, it appears, as they paid for her to go on a trip to the Walt Disney World Resort with the Tanner family, and in one episode, her mom even punished her by grounding her over at the Tanners. In the Season 2 episode Tanner vs Gibbler, D.J. throws a surprise party for Kimmy. When Kimmy shows up with her two friends from junior high, her companions converse about how they have trashed homes in the past at wild parties. They proceed to pick up the Tanners' phone and call friends (presumably party animals) such as "The Duke". D.J. angrily seizes the phone, tells him it's a "prank call", and leaves Kimmy with the decision to stay at her house or go with her friends from junior high to the mall. Kimmy chooses the older girls instead of D.J., despite the fact that they call her "Kammy" and don't seem to care much about her well-being (especially in comparison to D.J.). D.J. tries to guide Kimmy and steer her in the right direction by telling her they don't even say her name properly, to which Kimmy replies, "D.J., they wear lipstick! They can call me anything they want!" In the end, the two make up and continue their friendship. This is one of several tumultuous times during their friendship that Kimmy is to blame. Kimmy is known to snore and have smelly feet, and in many episodes, these issues are addressed. It is made clear throughout the series, even mentioned by Danny, that without D.J, Kimmy's life would have gone in the wrong direction.
D.J. met Kimmy in kindergarten, but the math from another later episode speaks of a friendship going back to when they were nine or so. It is imagined that age nine is when their being best friends started; perhaps this coincided with her moving next door. This is quite possible, because in the episode "The Trouble with Danny" from season 5, Kimmy remarks that her family would live in a place for five years, trash it, and then move out. Mentions of rollerblading in the living room and such lead one to believe that is true, while since they lived next door all seven years, something—most likely owning the home instead of renting—led them to take better care of it so they wouldn't have to move out. And, what would cause them to have the money to buy the house next to the Tanners? That is not certain, but the speculation is as wild as Kimmy's 1970s clothing, and one suspects the answer may be as strange as Kimmy herself. Their friendship hit hard times when D.J. was getting ready to go off to collage, and started caring more about Steve than her, but those issues were resolved.
While some household members can tolerate her, other members can't stand her. Stephanie and Jesse in particular dislikes Kimmy, who in turn teases her back quite a bit in the early seasons. Kimmy is not above teasing the other Tanners either. She calls Jesse "Hairboy" because of his perfect hair at times. Her nickname for Danny is "Mr. T", which he dislikes sometimes, telling her not to call him that. (However, in other episodes, he smiles at the nickname, not minding it at all.) Once she tried to play Breaking Up Is Hard to Do on their organ in the episode "Is It True about Stephanie?" after Danny and Vicky break up. However, the Tanners' biggest fear is her removing her socks as her stinky feet (which became a running gag during the later seasons) are her biggest means of torture for anyone.
However, underneath that comical, joking exterior is a true friend who is as much support for D.J. as D.J. is for her. Despite some arguments over the years—such as when D.J. fired Kimmy from her sports reporting job on the school paper for writing a paper that belonged in the gossip column instead, or when D.J. forgot her sixteenth birthday because it was also her six month anniversary of being with her boyfriend Steve—Kimmy remained a faithful and trusted friend right up to the end, when she brings Steve to the Tanners' doorstep so he can escort D.J. to her senior prom.
Danny is often seen telling D.J. "Please make new friends" from Seasons 3 to 5. But in the Season 8 episode Under the Influence, he says, "Well, D.J., I know I say a lot of things about Kimmy being an annoying, obnoxious nuisance, and I mean every one of them. But she's still your best friend".
Danny, Joey, and Jesse are usually very annoyed by Kimmy. But in the episode Those Better Not Be the Days from season 3 (where they look into the future and see what the girls are like as adults), Kimmy is portrayed as a woman who wears a tight dress and is good-looking. Then, after Danny says that their future doesn't have to be like that, and that they could all learn something from "that little story", as he calls it, Joey says, "Yeah. I'm really going to start being more nice to Kimmy Gibbler".
Kimmy is a straight D student and gets rejected by literally every college in California. She even attempted to bribe Stanford University's recruiters with twenty dollars, but got forty dollars back with her rejection letter, along with an additional message that said "Let's pretend this never happened". This forced Kimmy to look for other options, such as improving her grade point average by taking summer classes and attending community college.
She once worked as a movie theater attendant, but supposedly got fired after sneaking in Stephanie and Michelle in "Sisters in Crime". Luckily, she eventually found another job as a waitress at the Smash Club with DJ and Jesse.
There have been mentions of Kimmy's family, but they have never appeared on the show. Based on what she says about her parents, it seems that they are just as eccentric and strange as her. For example, in the episode On the Road Again in the final season, when D.J. wants to sneak off to see Viper and watch Jesse's band play, she asks Kimmy what she is doing that weekend, to which Kimmy replies "Going to the landfill to shoot rats with pop". In one episode she said she was happy her parents "stopped having kids after me". Plus, despite an early indication of having 3 sisters and a brother in the first season, the rest of the series focused only on Kimmy's frequent mentions of having just an older brother named Garth. Though from what she says about her brother, he is seemingly normal, considering the oddness of both herself and the Gibbler adults, one can only assume that Garth has his oddities. Because of Kimmy's frequent mentions of her family's eccentricity, it is assumed that is where Kimmy's overall personality and attitude comes from. Danny actually thinks she is good at driving.
According to D.J. in Our Very First Show, Kimmy has three sisters and her own room (which is seen in the episode The Apartment). Also, in D.J. Tanner's Day Off, it is revealed that Kimmy also has an older brother.
In the last season, she had a boyfriend named Duane, who almost always says "whatever". However, in the episode Up on the Roof from Season 8, when he is asked by D.J. if that is the only word he says, he replies with "I guess". (In the last episode, Kimmy mentions that he has a love for Shakespeare and he did recite a section from Romeo and Juliet). They were briefly engaged to be married, but ultimately decided against it when in Reno.
Over the years during Full House's run, Kimmy always had something to say -- which was usually often weird stuff, and often came up with zingers. Sometimes she revealed info about her family. Other times, she apologized to D.J. for when she did something wrong.