MONDAY: BEVERLY HILLS, 90210
YESTERDAY: DAWSON’S CREEK
TODAY: THE O.C.
LUKE-MARISSA-RYAN
How It Started: When bad boy Ryan moves next door, Marissa is instantly drawn to him even though she’s still dating her longtime boyfriend–and Ryan’s future enemy–Luke.
How It Ended: After Luke cheats on her, Marissa ends their relationship. Ryan and Marissa start dating soon after.
Key Episodes: 1.2, 1.4-1.9, 1.12,
YouTube Evidence: Ryan/Marissa/Luke–My Girl’s Ex-Boyfriend
THERESA-RYAN-MARISSA
How It Started: Theresa’s relationship with Ryan abruptly ends when he leaves Chino and moves into Marissa’s neighborhood. After a one-night-stand while he and Marissa are broken up, Theresa becomes pregnant and Ryan moves back to Chino to be with her in the first season finale.
How It Ended: In the second season premiere, Theresa tells Ryan she lost the baby, so he goes back to The O.C. and Marissa.
Key Episodes: 1.11, 1.20, 1.26-1.27, 2.1-2.2
YouTube Evidence: The O.C.: Look After You
ANNA-SETH-SUMMER
How It Started: Since he sees no future with his life-long crush Summer, Seth begins seeing Anna. This makes Summer realize her feelings for Seth, and he becomes torn between the two girls.
How It Ended: Just when it seems Seth has finally chosen Anna, he realizes Summer will always have his heart and commits to her. The relationship is tested again in the third season when Seth and Anna run into each other. But this time Anna actually works to keep Seth and Summer together.
Key Episodes: 1.4, 1.9-1.21, 3.22-3.23
YouTube Evidence: The O.C. Anna, Seth + Summer; The O.C.’s Love Triangle–Seth, Anna & Summer!
SETH-SUMMER-ZACH
How It Started: After disappearing and leaving her heart-broken in the first season finale, Seth returns to town to find out that Summer’s moved on to Zach. He then begins a series of attempts at winning her back.
How It Ended: Summer resists Seth’s advances and continues her relationship with Zach. When Zach and Seth team up to publish his comic book Atomic County, Summer is caught in the middle. Just as she’s about to go with Zach on a trip to Italy, Summer realizes she belongs with Seth and they reunite.
Key Episodes: 2.1-2.5, 2.10-2.14, 2.17-2.19, 2.21-2.23
YouTube Evidence: All or Nothing–Seth/Summer/Zach; The Way I Loved You–Summer/Seth/Zach
OTHER TRIANGLES TO CONSIDER
Ryan-Marissa-Oliver
Ryan-Theresa-Eddie
Kirsten-Sandy-Rebecca
Sandy-Kirsten-Carter
Ryan-Marissa-Johnny
Ryan-Tayl0r-Henri Michel
Bullit-Julie-Frank
TeenDramaWhore 
That sounds so glam & cool, getting to work at Seventeen! What was it like?
Ahh, the good old days of the OC 🙂
I thought the whole Anna-Seth-Summer debacle was awesome! And personally, I preferred Taylor with Ryan; he seemed to smile more then.
If you want Seventeen info, just e-mail me!
I generally liked Ryan and Taylor, too, but it seemed like something the writers did out of convenience and necessity. Ryan needed a love interest, so why not someone already in the cast? But it wasn’t in line with Ryan’s character and his “type.” Then again, they say opposites attract…