The InStyle shindig was the place to be post-Globes, so it looks like Sophia and Austin weren't exactly shy about keeping their blossoming relaysh under wraps.
So how did the two interact once they were inside?
"They were never more than five feet apart," an insider at the party tells us. "They were constantly at each other's side. She would chat with her girlfriends while he caught up with a few guy friends, but they were always next to each other."
As for any One Tree Hill PDA?
"They weren't overly affectionate," says our source, "but it was clear they were there together."
Hey, Danneel Harris, can we expect a double wedding happening anytime soon?
Another couple we also can't figure out at the bash was...
"They didn't interact at all," says a partier inside. "They arrived around the same time, and after he went inside the party Kate was pretty quick to follow."
However, there was zero PDA between the two while their night was just starting off.
"Kate was hanging with a few girlfriends outside in the smoking patio for a while, and Alexander held court at the center bar with a different blonde."
Our insider dishes that the duo didn't really come near each other the hour or so they were there.
Clearly that changed, because sexy Skars and an equally sexy Kate were seen sneaking in a few kisses at the HBO party at the end of the night.
Hey, get a few drinks in ya and old flames can be quickly rekindled when your night is wrapping up! Wonder if it was just some liquid courage bringing these two together, or if they're really into each other? We're still gonna take Alex's word that he's oh-so-single.
Also at the InStyle/Warner Bros. bash was...
Bradley Cooper sans his girlfriend (and rumored new roommate), Renee Zellweger. Don't think that let the Coop down, though. He was happy as can be hanging out with BFF Justin Bartha (accompanied by his girlfriend, Ashley Olsen) and a few other friends.
B.C. was overheard telling partiers that he was "shocked" The Hangover won Best Comedy. Bradley said he couldn't be happier about it, but that he wasn't even expecting it a little bit. He was also overheard laughing off and avoiding the question when someone asked him if he and R.Z. were really moving in together.
As for other party happenings at InStyle: Sandra Bullock and Robert Downey Jr. laughing and congratulating each other on their wins; Ashley Greene telling pals how excited she is to work with Sebastian Stan in The Apparition; Michael C. Hall relaxing with a few male friends most of the night and mingling with Kevin Bacon; Gerard Butler talking it up with various gals, and Cameron Diaz all smiles while catching up with Leo DiCaprio out on the smoking patio.
See how else the stars celebrated in our 2010 Golden Globes: Party Pics gallery.