Apparently, the original script had a completely different ending, according to Gossip Girl casting director Renee Godbout.
Below, Godbout described how Season 1 of Gossip Girl would have ended had they gone with the original script.
Serena & Dan
In the original script for the season finale, Serena (Blake Lively) does not catch Dan (Penn Badgley) hooking up with Georgina (Michelle Trachtenberg), but Dan confesses it to Serena anyway.
Godbout thinks the way the events went down in the version that aired was a better, more dramatic choice - it allowed S to call her nemesis a “crazy, manipulative bitch.”
More confrontation = more drama.
Blair & Chuck
The part of the “Much I Do About Nothing” script that was entirely rewritten involved Blair (Leighton Meester) and Chuck (Ed Westwick). They were supposed to rendezvous at the airport, not the helicopter pad.
Chuck gets stuck in traffic on his way to the airport because of a car accident en route. He sees Lily (Kelly Rutherford) at the scene, crying.
A stunned Chuck gets out of his limo only to find out that his father has been killed in the car accident.
Needless to say, Chuck doesn’t make it to the airport on time. Thinking that Chuck is back to his womanizing ways, Blair instead decides to spend the summer with Carter Baizen - the dude who bilked Nate (Chace Crawford) out of thousands at that poker game.
Godbout isn’t sure why the Gossip Girl powers that be decided to change the script. Perhaps they wanted to keep Bart Bass around to create more conflict between Rufus (Matthew Settle) and Lily.
there both so different
i wonder if Carter is going to return at all in season 2
and whether this means they dont plan to have Bart around for much longer