If you asked him, he wouldn't be able to say exactly when it started. To him, it just did, and they've just always been this way.
If you asked her, she'd smash you with a hammer. But later she'd admit to herself that there was a moment that it started. She remembers it perfectly, even though she can never place when it happened.
The first time, it was accidental. Justin was visiting, and Elliot moved to the center to give him his favorite spot. Susan just happened to be sitting closer to the center than normal, and their shoulders brushed. He immediately apologized, and they both moved away, but she couldn't help noticing how warm he felt.
The second time was very much on purpose. She was standing next to him in the hallway, and even though the football team rumbled past ten feet away, she still stepped closer to him. He felt just as warm as she remembered.
The third time was his fault. They were watching some stupid fantasy movie with overbearing rules of chivalry that the actors were hamming up, and he impulsively decided to make fun of them. He slid over the couch and wrapped his arm around hers, loudly declaiming in a bad accent about his honor. Halfway through his sentence, he stopped and threw himself back to his original position, stammering apologies. Her arm felt cold for the rest of the movie.
The fourth and fifth times didn't go unnoticed. Apparently they independently decided to both sit half-on the center cushion, moving them much closer. Their viewers jumped on it, commenting hundreds of questions about if or when they started dating. They quashed the rumors, but not without a little regret.
The sixth time caught him off guard. They were watching yet another movie that promised from the cover art to be terrible, but it was one of the most requested films yet. She came back with the popcorn bowl, and sat right next to him, close enough for their shoulders to brush. He just took the popcorn and didn't comment, even when she continued doing it for movies every time after.
Time six and a half was when she decided to make fun of the female lead and pretended to fall asleep on his shoulder. She almost didn't remove her head, because his shoulder was comfortable.
They were caught the seventh time. Elliot was just relaxing on the corner of the couch, with his arm resting on the back, when she sat down in her now-usual spot, not noticing where his arm was. Grace squealed, making them both whip around to face her. While hopping in place, she yelled about how cute they were together. Elliot tried to say something, but nothing came out, and his mouth just kept opening and closing like a fish. Susan wasn't much better, stammering out something about not being ready for a relationship. The two suffered through knowing looks for weeks.
The eighth time happened when he grabbed her hand to pull her out of the way of a rude bicyclist. He made as if to let go, but she held on. They stayed like that almost all the way to Tedd's house, then let go because one round of knowing looks was enough.
Elliot rationalized the ninth time. The heat was broken in the rental store, and she was shivering while trying to pick out the next movie to review. He wanted to help warm her up, so putting his arm around her was natural. And he didn't want to restrict her arm, so of course his arm went around her waist. And if she seemed to lean into it, that was only because she was cold.
The tenth time really shouldn't have meant as much as it did. There were no meddling friends around, so she had no qualms about sitting under his arm while watching a silly holiday romance. And so what if his arm slipped off the back of the couch? His arm made a good neck pillow. When the leads went into another sappy scene, it was only natural that she turn to him to make a sarcastic comment. But when she turned, his face was turned toward hers, mouth opening to make just such a comment. Their eyes met. Neither one of them knew who started the chaste kiss, but it only lasted for a brief second, before the faced forward again, cheeks burning.