While Seth Cohen, Ryan, Sandy, Jimmy Cooper and Caleb are in Las Vegas for a “bachelorette party,” Marissa discovers that Theresa is pregnant, father unknown. For a time Theresa reluctantly considered having an abortion, but Kirsten Cohen informed her that she still had a choice on the matter.
Daniel Diaz was a supporting character on “The O.C.”. He was portrayed by unknown. Daniel is the son of Theresa Diaz, she tells Ryan in Season 3 that she took a paternity test and the father is Eddie.
Marissa and Ryan’s relationship is strained again when Theresa comes to Newport Beach towards the end of the season after suffering domestic violence from her boyfriend Eddie. Theresa tells Marissa she’s pregnant and doesn’t know if the baby’s father is Ryan or Eddie.
Later in the season, on her 40th birthday, Kirsten found out she was pregnant. This reminds her of the time she was with Jimmy Cooper. During the big earthquake she is injured with bruises, but fortunately her unborn daughter was not hurt, the girl is then born in the final.
Just before New Year’s Eve, Summer is scared of pregnancy and Seth proposes to her. Despite Summer finding out she’s not pregnant, she and Seth decide to continue their engagement.
The year is 2027. Having moved to New York a long time ago (which essentially makes Seth’s yearly trips to ComicCon so much easier), Seth and Summer are busy raising their 15-year-old son he’s attractive but awkward and desperate to find out who he is.
On her first day at Harbor School, a lot of people taunted her for it. After Caleb’s heart attack, he decides to formally adopt Lindsay as his daughter.
Ryan rekindles his relationship with Taylor. Ryan and Taylor are now officially boyfriend and girlfriend.
A devastated summer tells Seth that “we’re over” during a beach party after announcing he won’t be going to her at Brown University in the fall. Seth insists he simply changed his mind, but he is actually lying to cover up the fact that he was rejected.
Theresa ends up lying to Ryan about her pregnancy and tells him that she lost her baby so he can return to Newport Beach and it is never fully explained whose baby she is secretly delivering . Ryan could have been the father, but it remains a mystery.
However, she tells Ryan, who meets Sandy’s expectations and returns home. Theresa comes to visit him and tells him that the baby is not his but Eddie’s. (However, it is strongly suggested that the baby is actually Ryan’s as it is seen with all the bright features like the young man).
In the Season 1 finale, Kirsten hints to Theresa Diaz, Ryan’s pregnant ex-girlfriend, that she had an abortion early in life.
He cheats on Summer A LOT.
Not only that, Summer has to come and save him from the pimp he owes money to…even though he kissed another girl. Later in the series, Seth goes on spring break and enters a whipped cream contest with a girl. On national TV, he kisses her and Summer sees.
Seth married Summer in the series finale. His other relationships were with Anna Stern and Alex Kelly. Seth’s goal was to attend Brown University, but he ended up going to the Rhode Island School of Design (RISD) and continuing to work on his comic Atomic County.
Then Kirsten becomes an alcoholic and also cheats on her colleague Carter Buckley. Although they both had affairs, the two realized that their love for each other was much stronger than any other relationship.