I Do (Lost) - Production

Production

"It's actually more difficult for her to stay in that house and cook breakfast and be a little housewife, than it is for her to break rocks and work in a quarry and sleep in a cage."

Show runners Damon Lindelof and Carlton Cuse wrote "I Do" as a "mini-season finale", as it was the last episode before mid-season hiatus, and would end in a cliffhanger. It also served as a climax and beginning of a closure of Jack, Kate and Sawyer's captivity on Hydra Island, with the writers saying that afterwards there would be a return to the beach and the six-episode block would be "more palatable" and make more sense, comparing them to the first seven episodes of season 2 where the tail section survivors are introduced. Executive producer Bryan Burk also said the pre-hiatus episodes were "our season 2.5. Like, this is kind of like wrapping up a lot of where we were last year", considering season three would really begin in the seventh episode.

A main theme of the episode is Kate's inability to commit to other people, always running from difficult emotional situations, and having barriers between her and her interests – physical, as in Sawyer's cage or Jack's aquarium, or metaphorical, as in her inability to settle down as Kevin's wife. Kate's marriage, which was first alluded in the season one episode "Outlaws", is meant to be a contrast with her relationship with Sawyer in the realtime events – Kate and Kevin is a heartfelt and passionate relationship where Kate tries to get involved but her lifestyle ends up on making the marriage fail, whereas with Sawyer both are afraid of intimacy and connection yet still end up together.

Nathan Fillion was cast as Kevin because the producers thought he fit as "someone to believe that Kate had actually married and settled down with" for being "really good and kinda fun and intelligent", and also because Cuse and Lindelof were fans of Fillion's work on Firefly. Fillion said that he was a Lost fan and described his experience working at the show as "a dream".