ER: Here's the real reason Carter and Lucy never got together

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Although John Carter and Lucy Knight had palpable chemistry on ER, the show never brought the two together in any official capacity, much to the disappointment of millions of viewers — and now we know why.

Kellie Martin joined the show in season 5 as third-year medical student Lucy Knight, who was assigned to work under Dr. Carter (Noah Wyle) in what ended up being an often contentious relationship that eventually bordered on mutual respect. But fans were immediately drawn to the duo and — as the kids say these days — ‘shipped the two of them romantically.

However, Wyle was adamant that the show never act on Carter and Lucy’s unspoken chemistry. “Never. Is that definitive enough?” Wyle tells EW.

The two characters did end up briefly kissing in a season 5 episode, with Carter immediately shutting down their potential romance because she was his student. But when Wyle found out Carter and Lucy were supposed to do a lot more than kiss, he went to the source to shut it down. “I thought of her as sort of a little sister, which is why when they wrote this episode for us to suddenly start making out in this room, I had such a huge problem with it,” he says. “The script originally had us having sex in one of the exam rooms, and somebody walking in on us. I had a big problem with it. In fact, in the 15 years I was on that show, the 260-some-odd episodes I did, I only wrote [executive producer] John Wells one letter asking him to change something that he had written, and it was about that episode.”

“I just thought Carter wouldn’t do it, he wouldn’t do it at work, and he wouldn’t do it with this student, and he wouldn’t do it with her,” Wyle says. “He wouldn’t do it, he wouldn’t do it, he wouldn’t do it. So I made this huge passionate plea to John about how the character’s ethical center is his core defining characteristic, and once you infringe upon that or you chip away at it, it’s very difficult to get that back. I went through this whole thing and he was so amused by my letter that he proposed a compromise of this kiss.”

Wyle is quick to point out, however, that his opposition to the couple had nothing to do with Martin. “Not that Kellie is not a very attractive woman,” he says. “She is, she’s adorable, and anybody in their right mind would find her so. However, I felt that John Carter, in that moment, he liked a different type of woman. She’s a good kisser. I’ll give her that. It wasn’t unpleasant to shoot, but I kind of wished we hadn’t.”

For her part, Martin was “definitely sad that Lucy and Carter were never an official couple,” the actress says. Martin even says she still has fans who reach out to her on Twitter lamenting that Lucy’s death meant the character would never be Carter’s wife. “It would have been really fun,” she says. “And I think that they had intended for Lucy and Carter to be together in the beginning, but when you start a story line, you don’t know where it’s going to end up. It’s such a puzzle, and it’s maybe those two people who were friends, and should have gotten together but they didn’t. That happens in life so often, and it feels like that’s how it actually was on ER with Lucy and Carter.”

The actress says that much like Lucy followed Carter around, so too did she with Wyle during production. “He knew how to do that show so well, because he started at the beginning, and there was definitely a rhythm and a speed at which you do that show, when you just rattle off that medical dialog, which I never found easy,” she says. “So I was just like this little puppy tagging along behind Noah the whole time, and it definitely more felt like a friendship between Lucy and Carter than it felt like any kind of romance.”

Following Lucy’s death in season 6 — which you can read all about here — Carter went on to have a relationship with Abby (Maura Tierney), who joined the show a few episodes before that infamous hour in which Lucy and Carter are both stabbed. “I think one of my favorite people — and I called her my replacement to her face, and she was fine with it — was Maura Tierney,” Martin says with a laugh. “I’ve run into her since, and I have such a great respect for her, so if somebody had to replace me, I was really happy that she was the one who did it.”