Many of you may know that Blake Lively doesn't drink. But do you know why? At least one reason is that until today, she wasn't 21. (We know, you thought she was 30.) But on this gray Monday morning, the girl that brings sunshine to Gossip Girl is finally legal. Last night, several of her fellow castmembers were at Henri Bendel for a YSL party celebrating the show. Shockingly, some of them didn't even know what an important day today was! (Thank God there are creepily obsessed fans like us to remind them.)

There's an official birthday party a few weeks away, but what are people doing today?

• Producer Amy Kaufman has a surprise in store. She promised it wouldn't be as over-the-top as last year's present (a man dressed up in a chicken costume).
• "We'll probably get her wasted," said Dreama Walker (who plays Hazel, duh). "Everyone is always like, 'Oh you're 21, let me buy you a shot!' Say no. Just say no. It doesn't feel good the next day."

• Taylor Momsen won't be doing too much celebrating of Lively's big day, she said. After all, she's only 15.
• Leighton Meester looked vaguely annoyed when we even brought up the topic. "We're working together early in the morning, so, that's kind of sad," Meester sniffed. "I'm going to be there right when she's turning 21." What is she going to get her? "That girl has everything," Meester said, with a wave of her hand.
• Matthew Settle and Kelly Rutherford (a.k.a. Rufus and Lily) wanted to give her advice, but didn't have any. "Everything you're doing is perfect!" says Rufus. "Stay that course. Stay that road." "She seems to be doing everything right," Lily chimed in. "I am going to ask her for advice!" Sure, you have to say that, Lily. You're her mom.