Casey Gardner and Izzie both go to the same school. This is where them two meet. When they first meet, Izzie is shown to be rude to Casey. They later get on really well while in detention. However, Izzie pushes Casey away, because of an incident with Nate (Izzie's boyfriend). Later is Season 2, Izzie goes up to Casey's room (on Casey's 16th birthday). Izzie wants to be friends again and says "Lets forehead promise, to never leave each other again." They put their foreheads together and lean in for a kiss. But, they are interrupted by Casey's mother (Elsa Gardner). In the last episode of Season 2, Casey and Izzie meet up and are sitting in Casey's car. The two hold hands, while sitting there silently.
Casey meets Izzie on her first day at Clayton Prep after transferring from Newton. Izzie is far from welcoming. When they first meet, Izzie is shown to be rude to Casey. stating she knows what happened at Casey's last school and what she heard wasn't good. Izzie says she doesn't want any drama which Casey agrees with before Izzie leaves her to fend for herself instead of showing her around like the coach had expected. Even though Izzie was rude, later on at track practice she is shown to be a little sympathetic towards Casey asking if she made her way around alright. Izzie also notices the state of Casey's trainers when a team member points it out and doesn't join in with the rest of the team when they laugh at Casey's comment about going to Target during the summer.
Later on in the episode, as Casey becomes friends with a boy called Nate who is revealed to be Izzie's boyfriend, he explains how Izzie is threatened by Casey because she is faster than her.
Izzie and Casey are at track practice when they begin to race one another after Izzie makes a comment about Casey slowing down. They both begin sprinting down the track when Izzie falls and injures her wrist accusing Casey of tripping her up. They both end up getting detention because of this.
In Coach Crowley's office, Casey and Izzie are told they are not to leave until they get along. After the Coach leaves, Izzie asks Casey to get her phone because of her injured wrist still blaming her for the incident. Hearing Izzie mention a baby whilst on the phone, Casey asks if Izzie has a child which reveals she looks after her three younger siblings at home; one of which is a baby. With this in common, it allows Casey to open up about Sam being autistic and they are finally able to bond.
As they open up to each other, Casey admits she doesn't think she will get out of the town because her dad and Sam need her around. Izzie steps out the room for a second coming back with a bottle of Vodka she stole from a teammates locker stating she's tired of being perfect constantly and suggests they stop caring about everyone else. They share the vodka when Izzie opens up that she spends so much time with Nate because she doesn't want to go home and things don't feel quite right with him. This was the first sign of Izzie's possible sexuality. Casey, however, stated she doesn't feel that way with Evan.
Izzie walks up to Casey saying she needs her because her mother's ex-boyfriend has moved back into the house before asking where Casey has been. She puts it down to life stuff to begin with before opening up about her father's panic attack which they assumed was a heart attack. Izzie jokes that it's a miracle they are still alive before being interrupted by Nate.
Walking in to join Nate and Izzie, Casey complains about still being hungry. Izzie teases her saying she should have ordered pizza before Casey confesses to not liking the pizza describing its taste as 'a stale cracker with ketchup on it'. She explains that she's spoiled due to having a great pizza place near where she lives. Izzie suggests they go there on Friday with the team and Nate agrees leaving no room for Casey to disagree. Later on when Casey is hanging out with Evan and mentions the meet up, he asks if he can go which Casey agrees to.
Izzie and Casey are seen laughing and joking with the team when Evan arrives. Izzie asks 'Newton, is this him' when Casey jumps up before she introduces Evan to everyone. They all talk about how Izzie was mean to her when they first met and that Nate was Casey's first friend at Clayton which Evan didn't know about causing tension between the couple.
Izzie turns up at Casey's house upset after an incident with her mother's boyfriend throwing things around the house. Casey immediately hugs her in comfort. Izzie explains what happened with her mother's boyfriend stating she told him to leave before taking the kids out of there when he began throwing things taking them to her grandma's. Casey tells Izzie she is staying with her after Izzie says there isn't a lot of room at her grandma's place. Not long after, Sam walks through the door where Casey introduces them before following Sam up the stairs when he states he has no time. When Sam feels unsure about going to sleep at Zahid's house without Edison there, Izzie suggests he take his food and leave Edison where he is comfortable. Casey is seen smiling afterwards.
In the living room, Casey is reading a Stephen King novel to take Izzie's mind off everything, which they put down as it becomes too scary. Izzie thanks Casey for building the fort before Casey offers staying in there forever if she wants. Izzie admits that Casey is her favourite person, even if it sounds lame, which Casey says back and states that Izzie can't tell Sharice in a joking manner.
Later on, there is a knock at the door which Casey jokes about it being 'Pennywise'. Izzie confesses to texting Nate which is why he turned up and suggests watching a movie. Casey turns around to say she will fall asleep which is shown to be right as she is seen sleeping when Nate has been let in. As Nate and Casey talk and she thanks him for being her first friend at Clayton he leans in kissing her. Casey pushes him away instantly stating they will never happen and kicks him out. Casey is later seen laying in bed next to Izzie wide awake as she sleeps.
After the incident with Nate last episode, Casey writes Izzie a note after being too scared to tell her in person. Just as she's trying to put the note in her locker, Izzie walks around the corner joking about it being a love note for her. Casey tries to hide the note but Izzie pries it from her fingers reading it in front of her with Casey stating she wanted to tell her in person but chickened out. With Izzie's mixed emotions, Casey offers to go somewhere to talk about it which Izzie declines saying she needs time to think before walking away.
Casey is seen talking to Evan about it in her room. In reference to Izzie, she says 'I like love her. We got so close so fast'. She then goes on to say that she and Izzie are so alike and hopes they will be okay. This is the first time Casey has stated how much she cares about Izzie. It is unclear at this point if she references her friendship or her possible feelings. However, you can see the evident worry on her face about them not talking.
The next day, Casey tries talking to Izzie who brushes her off and reveals she hasn't broken up with Nate but is in fact taking his side since he stated Casey kissed him instead and she has known him longer. Izzie says she doesn't know what to believe and even though Casey tries to get Izzie to believe her, she says 'back off, Casey' instead of using her nickname,'Newton' before walking away with Nate. This is the first and only time Izzie calls her this. Casey, upset, storms off down the hallway in the opposite direction.
Casey mentions Izzie at the start of the episode when she is seen getting Evan to try dipping cheese in apple juice. He teases her saying she misses her friends which she denies but then admits 'Izzie would have loved this though.' Later, Casey is seen getting ready in the locker room but when she gets her trainers out the locker, they have the words 'Slut' and 'Hoe' on the toes and when she tries to rub it off with a paper towel and water, it doesn't work. Casey is seen emotionally distressed at this. It is unclear whether the track team did this or Izzie herself. When Elsa finds out what happened to her trainers, she buys her a new pair.
- They both have responsibilities to their siblings. Izzie looks after her three siblings at home because of her mom's issues and Casey looks out for Sam constantly because of his autism.
- They are both athletic and strong runners.
- They are each other's favourite person.
- Izzie is the first person shown that Casey has openly introduced to Sam without any doubt.
- They are the first possible LGBT characters to be seen on the show.
- Neither of them are like any of the other students at Clayton Prep considering they are both there on a Scholarship.