Oh, P and B. We really thought that of all the couples amongst the Gossip Girl cast, these two might just go the distance. But alas, Penn Badgley (Dan) and Blake Lively (Serena) are no more.

What torpedoed their romance? Allow us to speculate.
Credit: PacificCoastNews Photo: Blake Lively and Penn Badgley Kiss on Set on September 23, 2010.
1. Ryan, Ryan, and Ben. Rumors have flown fast and furious about Blake and her male co-stars Ryan Reynolds and Ben Affleck. Even if they’re not true, that sort of thing has to put a strain on a relationship. And she did start dating another Ryan (Gosling) awfully fast after their breakup.

2. A star is born. When Gossip Girl began, these had two had roughly equal amounts of fame — which is to say, not very much. But in the last year or so, Blake has broken out in a big way. She’s appearing in a slew of blockbusters and she’s the darling of the fashion world — she needs A-list arm candy at her side. Penn, sadly, does not qualify.

3. He got tired of being upstaged by her hair. Not to mention other well known parts of her anatomy.

4.She stopped finding blinking and sheepish back-of-the-neck rubbing charming. We would never stop finding that charming, Penn! Call us.

5. They realized that they weren’t actually their characters. Sometimes as an actor, it’s hard to differentiate between work and real life. Maybe one day they both woke up and realized, “Hey — we aren’t Serena or Dan. We don’t have to date.”