Carly Shay (Miranda Cosgrove) lives with her older brother, Spencer, in Seattle, Washington.
Carly's best friends are Sam Puckett, Freddie Benson and Gibby Gibson. Carly lives in the "Bushwell Plaza" in apartment 8-C with her funny, often careless, artist brother Spencer Shay.
In "iPilot", Carly takes the heat for one of Sam's pranks and has to oversee people who want to be in the school's talent show. When Carly, Sam, and Freddie's suggestions are completely ignored, they decide to make a web show named iCarly upon Freddie's suggestion, with the 'i' standing for 'internet' and Carly's name since she will be the host of the show.
Carly is a smart, pretty girl who gets good grades, going for straight A's in one episode. She is kind and naive at times, wanting to believe the best in people. She has her moments when she proves just how crazy she can be. Yet in many ways, she is more grown up than her adult brother.
She has occasionally wondered why she and Sam are friends as Sam tends to get her into trouble. Freddie has a crush on Carly, which everyone is aware of. However, she does not feel the same way (which she has told him many times). Despite this, in "iSaved Your Life", Carly wants Freddie to become more than friends because Freddie pushed her out of the way of a truck, getting hit himself instead. Although he was originally eager about their new relationship, Sam later advises him to break up with her. Freddie does so but regrets it later. In "iSpace Out" and "iSam's Mom", it is seen that Carly is claustrophobic. Carly was a vegetarian at one point.
She is the younger sister of Spencer Shay and the daughter of Colonel Steven Shay and Mrs. Shay. She lives with her older brother, Spencer, in Apartment 8-C at Bushwell Plaza in Seattle while their father is stationed on a Navy submarine; their mother has never been seen and was only spoken of once when it was stated that she was in the armed forces. She is the best friend of Sam Puckett and former best friend of Missy Robinson whom she hung out with during her childhood. She is also the best friend of Freddie Benson who lives across the hallway (Apt. 8-D) who has had a crush on her since the day they met. Carly is a kind, easygoing, and caring person who would do anything for her friends, although she can be spoiled at times when she doesn't get her way, especially in "iLook Alike", when Spencer would not approve her going to a mixed martial arts fight, which causes her to go into a tantrum state. In "iDate a Bad Boy", it is shown that she can be shallow, as she had a dislike of Griffin's hobby of collecting Pee Wee Babies (a parody of Beanie Babies).
Occasionally, she is forced to mediate between her best friends, Sam and Freddie. She usually tries not to get in trouble, except for when she takes the blame for Sam's wrongdoing. However, when pushed too far, like in "iHave My Principals", Carly has proven to be just as devious as Sam, which catches most people by surprise because of her generally nice demeanor and the little-known, but generally assumed, fact that she has never pulled a prank by herself until "iGet Pranky" (which she did with Spencer's help).
It was shown in iSpace Out and confirmed in iSam's Mom that Carly suffered from claustrophobia and freaks out when she is locked in a small space for a long period of time; in iPsycho, she appears distressed when Nora locks her, Sam and Freddie in her booth down in her basement.
Possibly her most prominent trait, Carly is not tough, and even when furious, she has never physically attacked anyone on-screen (but tried to tackle Freddie in an angry manner in "iThink They Kissed" and "iPromise Not to Tell"). However, on occasion, she will confront someone, even bullies and teachers, as shown in "iHave a Lovesick Teacher" and "iMake Sam Girlier". She was also part of a girl mob (Sam and Shelby Marx) that beat up Nevel in "iFight Shelby Marx" although Nevel said he wasn't scared of her.
Carly shows singing ability in "iDo", when she sings Shakespeare, and in "iPie", when she tries to get people at a funeral to sing "Amazing Grace".
In "iParty with Victorious", Carly portrayed a character called The "Hideous" Patty Schwab, Carly disguises herself to prevent recognition from fans so they can focus on finding Steven (Carly and Tori's boyfriend). Patty had a British accent. She said she was "Hideous" because of her look, along with Sam and Freddie, who also wore disguises. It is shown that she wears a mask to keep her from snoring. And in "iMeet the First Lady", her father's pet name for her is "Snug Bug." She has a liking for Bad Boys and Kissing boys. She moves to Florence, Italy in the series finale. Although her name is not stated, She is once mentioned in the show Sam & Cat when Sam states her best friend moved to Italy with her dad. She was never mentioned again until the episodes #The Killer Tuna Jump: #Freddie #Jade #Robbie when Mrs. Benson walked in on Freddie while he was talking to Cat over the phone in the hallway. She asked him if he was staring at Carly's apartment door again and reminded him that she was still in Italy with her dad and that she will never love him, and also in the episode SuperPsycho when Nora asks Gibby where Carly is so she can take revenge, Gibby mentions Carly being in Italy with her dad. She is also mentioned when Nevel is in the Mental Institution and he asks about Carly's mother.