[3] Marissa is introduced as a wealthy, beautiful socialite in Newport Beach, California, whose family (mother Julie, father Jimmy, and younger sister Kaitlin) go through dramatic changes over the seasons.

Schwartz said that the network was "nervous" about the storyline and wanted it "wrapped up as fast as humanly possible and Alex moving on out of the OC.

Luke Ward, Marissa's long-term boyfriend, shows animosity towards Ryan from the moment he steps foot into Orange County.

Soon after, on vacation in Tijuana with Ryan, Seth Cohen and best friend Summer Roberts, Marissa discovers that her parents are separating.

Marissa and Ryan's relationship is strained once more when Theresa comes to Newport Beach towards the end of the season after suffering domestic abuse from her boyfriend Eddie.

In the season finale, Ryan leaves Marissa to move back to Chino and help Theresa raise the baby.

At Jimmy's farewell party, she confronts her parents in public and loudly calls Julie a whore and herself "the daughter of a thief and a slut.

Seth is initially reluctant to tell his foster brother, knowing Ryan's volatile temperament and tendency to physically lash out when it comes to people he cared about.

As the series' third season opens, Marissa is under investigation regarding the shooting of Trey Atwood, who is in a coma as a result of the wound.

When he awakens, Julie threatens to smother Trey if he does not tell the authority that Ryan shot him, in order to keep Marissa out of trouble.

Ryan is let free, and Marissa faces no legal liability as she was defending another person's life using proportional force in the circumstances.

Despite a lack of legal repercussions, the event results in Marissa's expulsion from the prestigious Harbor School, as it is cited along with her past of flagrant shoplifting and substance abuse.

This results in Johnny falling to his death from a cliff after a drinking binge, and the tragedy causes Ryan and Marissa's final breakup.

In the wake of Johnny's death, Marissa struggles to find closure, as well as her own place and purpose in Newport Beach.

In the season finale, Marissa receives a letter from her father inviting her to live for a year on a boat with him in Greece, and she accepts.

The day she graduates from Harbor along with her friends Summer, Ryan, Seth, and Taylor, Kevin begins calling her and asks to see her, but she declines.

In the episode "The Cold Turkey", Julie decides that it was time to move on after learning that Volchok turned himself over to the police and had been arrested.

Later in the episode, during Thanksgiving dinner, Ryan reminisces to Julie about the first time he saw Marissa out on the driveway and thought that "she was really hot".

where Ryan and Taylor Townsend, both in comas, enter into an alternate universe where he has never moved to Newport Beach, and the lives of most major characters are completely changed.

She surprises Julie's maid, who tells Taylor that "Miss Cooper's" plane arrives at 3 o'clock from Berkeley.

Although extremely on-and-off-again throughout the show's course - their relationship originated as a platonic friendship in the pilot episode, which later escalated into romantic feelings.

The third attempt of Marissa and Ryan's relationship terminates after the suicide of Johnny Harper where they struggle to mourn him and need a break from each other.

[10] The overall relationship between Marissa and her mother, Julie Cooper, is full of angst, rebellion, misunderstanding and miscommunication.

Beginning with the fling between Julie and Marissa's ex-boyfriend Luke Ward, the strain in the two's relationship increases throughout the course of the show.

The troubled Marissa is then left to deal with her friendship, alcoholic, and depression issue alone, without the help of Julie.

The friendship between Summer and Marissa is further strengthened by the boyfriends they often have: best friends, and “brothers,” Seth Cohen and Ryan Atwood, as many group hang-outs and double dates occur.

Their friendship offers strong signs of female solidarity and is unique in that it is shown as a source of support and a catalyst for empowerment.

Marissa and Luke's relationship stems back to the fifth grade on a class trip to the Museum of Tolerance.

Issues in Marissa and Luke's relationship constantly arise, making the viewer question if they really are in love.

On a trip to Tijuana, Marissa discovers Luke cheating on her with one of her friends, Holly Fischer, on the dance floor in a club.