Ian (Daniel Augustin) seems to represent what Ted had with his ex Victoria. Even though they came so close to being together a couple of times, they just weren't each other's lebenslangerschicksalsschatz (a German phrase that means "lifelong treasure of destiny").
Similarly, Sophie and Ian seem like endgame in a lot of ways, but something always gets in the way. Ian spent most of season one on the other side of the world, only to return in the finale. But in the first episode of season two, things don't work out with him again as Sophie tries to make sense of the romantic minefield she's found herself in. But, since Ian likes Valentine's Day and doesn't appear in that episode, he comes in pretty high on the list. Near the end of season two, we also find out that he is back in New York and working at Columbia — though he's in a new relationship. It seemed likely he would return in season three to cause more chaos.
