Ellie and Sean started dating in Take On Me after trading secrets and bonding over their mutual distaste for how others viewed them without knowing them. While they were a good fit, Ellie entertained the idea of dumping Sean, as she felt he was rude to her best friend Marco Del Rossi. Alternatively, Sean felt that Marco didn't give the couple enough space. Ellie moved into Sean's apartment after her mother passed out drunk and started a fire in their home in Our House. After the school shooting, Sean moved back to Wasaga Beach to be with his parents, leaving Ellie and their relationship behind.
In Karma Chameleon, despite the fact they didn't interact with each other Ellie is sarcastic but seemingly sympathetic towards Ashley after Sean blows her off.
In Careless Whisper, Sean catches sight of her and asks if Marco is actually with her in which he responds by kissing her.
Season 3In Take On Me, Ellie and Sean are serving Saturday detention along with Jimmy Brooks, Hazel Aden and Toby Isaacs. Coming from completely different social cliques, the five of them find it difficult to get along at first but boredom leads them to all form a temporary bond. Sean and Ellie, in particular, begin to talk and relate to each other as misunderstood individuals though Ellie assumes Sean is someone pretending to be deep & meaningful to get with her so she uses it to her advantage by acting like this misunderstood person though the more they talk the more they discover something about each other. From there, a mutual trust builds up between them as Sean confesses to Ellie that he and his clique have stolen valuable items from the school and Ellie shows him the scars on her arm due to her cutting issue. He looks at her cuts while they lay down with each other, and while her arm is up still in the air, he moves his arm and he gazes her cuts with his fingers, only for him to smoothly intertwine his hands with hers, leaving them happily holding hands with each other. However, shortly after Mr. Raditch decides to release them from detention, the trust is quickly destroyed once Sean, Jimmy, Hazel and Toby catch Ellie recording their conversations via tape to use for an article she planned to write for her co-op job. Everyone is angry with Ellie, especially Sean who quickly drops (the wrong) tape onto the floor and crushes it beneath his foot. When they return to school on Monday, Ellie finds Sean, apologizes for what she did and gives him the real tape, stating that she's not going to write the article. Sean forgives Ellie and the two of them began dating.
In Don't Dream It's Over, Sean is annoyed with Marco Del Rossi's presence as a third wheel to his new relationship with Ellie. Ellie tries her best to balance time with her best friend and boyfriend, even if it means bringing Marco on a movie date with Sean and herself. However, when Sean acts exceptionally rude towards Marco by sitting in between him and Ellie, pushing him away, Ellie angrily walks away. Later, Marco surprisingly advises Ellie to give Sean another chance as he could potentially be good for her. Prior to dating Sean, Ellie's first taste of a relationship was merely a cover as she was only dating Marco to hide the fact that he is gay. Therefore, Ellie admits to Sean that she isn't quite experienced enough to know how a real relationship is supposed to work and she wants Sean to show her how. When Sean agrees to do so, they kiss and make up.
In Our House, Sean regretfully reveals to Ellie that he and his brother are relocating to Alberta, which means they have to break up. Suddenly, Sean discovers an alternative; he can stay at Degrassi, collect student welfare and keep his apartment. Just as Ellie suggests that she and Sean can maintain a long-distance relationship, he tells her that it wouldn't be necessary because he's staying. Of course, both of them are extremely happy. In celebration of his new independence, Sean begins to frequently host parties at his place with regular guests including Ellie, Jay Hogart, Alex and his ex-girlfriend Amy, who is clearly jealous of Ellie. However, things begin to spiral out of control and it threatens Sean's new, comfortable life. Amy was taken away from his apartment via ambulance due to severe alcohol poisoning; but luckily, she survived and Sean was saved from losing his student welfare. During those incidents and even Sean's apologetic confession in The Power Of Love about stealing Mr. Simpson's laptop, Ellie has proven to be a great girlfriend and tremendous support system to Sean. Their relationship continues for several more months.
Season 4In Anywhere I Lay My Head, Sean invites Ellie to move in with him because he loves her and he knows firsthand what it's like to live with an alcoholic parent. At first, Ellie is reluctant to abandon her mother until she wakes up in the middle of the night to find the kitchen on fire while Mrs. Nash is drunk and unconscious at the table. So, Ellie has a change of her heart and decides to move in with Sean while Mrs. Nash was under the impression that she was actually staying at Ashley's place. The following night, while Sean and Ellie are hosting a housewarming party, Ellie is nearly emotional as she tells Sean that she doesn't want to go back to her mom and Sean assures her that she doesn't have to. Suddenly, Mrs. Nash angrily shows at Sean's place and orders Ellie to come home with her as she found out from Ashley's mother that Ellie hasn't even been staying there. When Sean tells Mrs. Nash that Ellie is better off with him, she promptly slaps him and tells him to stay away from her daughter. Shortly after, however, Ellie(with a new pet ferret) returns to Sean and informs him that her mother allowed her to come back. After seeing the cutting scars on Ellie's arm, her mother broke down and realized what her drinking habit was doing to her daughter.
In Mercy Street they're both against Emma's silent protest and believe it's gonna blow up in her face.
In Islands In The Stream, Sean and Ellie are briefly seen sharing a romantic moment in the cafeteria while Paige was sitting from a distance commenting on how their relationship is progressing while her own relationship with her longtime boyfriend is suffering.In Back In Black, emotions are running high during the aftermath of the school shooting that left Jimmy Brooks paralyzed and Rick Murray dead. Ellie tries to get Sean to open up to her about his feelings but he resists her and keeps his guilt and trauma bottled up inside. In an effort to "express himself", Sean makes a rash decision to confront his parents back at his hometown, taking Ellie, Jay and Emma along for the ride. As a result of the emotion that he was trying to keep concealed, Ellie sees Sean acting out in many different ways including telling his mother off, getting into nearly violent altercation with his former enemy and nearly drowning after a jet ski accident, only to be rescued by said enemy. Ellie could feel her relationship with Sean going down the drain as he continues to refuse to open up to her. Instead, he is repentant to Emma for the pain he's caused her the previous year and he also decides to reconcile with his parents by breaking down emotionally, confiding in them the guilt he feels over Rick's death. When Sean ultimately decides to stay in Wasaga Beach with his parents, it breaks Ellie's heart and she begs him to stay. Although he loves Ellie, Sean has made up his mind with no intention of changing it. Alas, Sean and Ellie part ways with tears in their eyes, thus, ending their first and only relationship together.
In Neutron Dance, Ellie is seen packing up her and Sean's apartment. She tells Ashley that guys suck, and enjoy messing with your feelings before leaving you alone to pay the rent, referring to Sean.
In Here Comes Your Man (2), Emma told Sean that since he and Ellie were "hot and heavy for a while," he should consider pursuing another relationship with her. However, Sean said, "Forget Ellie. I know who I want. I think you do too," referring to Emma herself.
In Eyes Without a Face (2), Ellie confided in Ashley that she and Sean had never had sex and, consequently, she was still a virgin.
In Don't You Forget About Me, While sitting at The Dot, Ellie answers a phone call, which turns out to be from Sean, an ex-boyfriend of hers. She is surprised to hear from them, as they haven't talked in a year. She tells him to look down the bar, where it turns out he is sitting, calling her from behind a menu he was hiding with. He hugs her hello and tells her that she looks amazing. Looking uncomfortable, Ellie stares at him, and Sean apologizes to her. She tells him he looks good as well, asking what brings him back to Toronto from Wasaga. He tells her she is opening up his own shop to customize bikes, and Ellie is impressed. Sean tells her that he has grown up and is going after what he wants, implying it is Ellie. Ellie shuts him down, saying he is the guy who bailed on her with an apartment she couldn't afford. She is still pissed, and Sean apologizes again, saying that he had to go home after the shooting to think about things. He tells her a lot of things have changed, but not his feelings about her, as he still cares about her. Sean leans in and kisses her, but Ellie tells him that when he moved to Wasaga, she moved on. She tells him she likes someone a lot, referring to his former friend Craig Manning. Ellie tells him goodbye, wishing him luck with his bank loan for his shop. After she leaves, Sean rips up the papers for his bank loan.
In What If Jimmy Was Never Shot, Sean and Ellie are sitting down at a lunch table, while Ellie discusses different colleges she might want to attend. Sean seems to not be listening, however. Jimmy announces that he won a basketball scholarship, and everyone is happy for him except for Sean. They start talking about the different clubs they're gonna go to, when Sean says that they're probably not gonna let him in. Ellie says that he doesn't know that, but Sean denies it and rolls out of the table in a wheelchair. He says that they can go without him, and Spinner, Craig, and Jimmy leave. Ellie stays and says that Sean can do "anything he sets his mind to". The two hold each other's hands and smile at each other. Since Jimmy was never shot, this caused Ellie and Sean to never break up since he never moved back to Wasaga.
In Party Etiquette, Ellie sees Sean at Marco's party, and assumes he is there to see her. She changes her outfit before approaching him and making out with him. Sean pulls Ellie off of him and tells her to calm down. Emma asks Sean what's going on. Sean tells her he came here to talk to her, and she tells him that it's hard to talk with Ellie's tongue down his throat.
- Ellie was two months older than Sean: she was born in August 1988 while he was born the following October.
- This couple was one of three relationships to start in detention. The other two were J.T. and Liberty and Jimmy and Hazel.
- They started dating in the same episode as Jimmy Brooks and Hazel Aden (Take On Me).
- They lived together whilst they were still in school.
- Ellie remained in the home once shared by Sean and his brother after Sean departed Degrassi, and returned to his hometown.
- In Love My Way, Jesse said to Paige Michalchuk that Ellie hates dancing, but she used to dance with Sean.
- Ellie was Sean's third girlfriend on the show after Emma Nelson and Amy Peters-Hoffman.
- Sean kissed Ashley Kerwin, one of Ellie's best friends.
- They were both friends with Alex Nuñez.
- Their first on-screen kiss wasn't until Don't Dream It's Over.
- They both attempted suicide by drowning: Sean in Back In Black and Ellie in Degrassi Goes Hollywood.
- Emma tried to encourage Sean to pursue Ellie again in Here Comes Your Man (2) but he was not interested in doing so.
- Ellie was later romantically interested in Craig Manning, who had been friends with Sean.
- Ellie was good friends with Jimmy, who previously had a conflict with Sean. Jimmy had an unrequited crush on Ellie.
- Sean was formerly friends with Marco Del Rossi, Ellie's best friend and ex-boyfriend.
- Ellie had a conflict with Sean's friend Manny Santos.
- After Sean left for Wasaga, Ellie continued to stay in the apartment, struggling to pay rent until she returned home in Queen of Hearts.
- As revealed in Eyes Without a Face (2), Sean and Ellie never had sex.
- They each had alcoholic parents: both of Sean's parents Mr. Cameron and Nona Cameron were alcoholics, which led him to live with his elder brother Tracker Cameron, while Ellie's mother Caroline Nash's alcoholism led her to cut herself.
- While Sean was very knowledgeable about cars, Ellie knew almost nothing about them.
- They were both originally members of the Class of 2006. While Ellie graduated with that class in High Fidelity, Sean was held back in Eye of the Beholder and was expelled in Here Comes Your Man (2).
- Sean's friend Toby Isaacs thought that Ellie was attractive.
- Sarah Barrable-Tishauer favors this couple.
- Like Ellie's father Colonel Nash, Sean served in the Canadian Army.