"This is the greatest party I've ever had," Diddy, wearing a cotton-candy-pink button-down shirt, told the crowd. "I'm so excited to have girls, but I know I'm in trouble now!"
Guests including rapper LL Cool J and socialite Denise Rich feasted on shrimp, pink cocktails, specially made pink M&Ms and Perrier Jouet champagne in pink floral bottles.
There were also gifts galore – a pink and white Ga Ga Designs chandelier from Denzel Washington, a custom-made changing table from Jay-Z and two cream-colored cribs from LL Cool J.
One thing still on Diddy and Porter's baby registry: an $88,000 R-class Mercedes Benz. It's "for the twins to ride in," Shalena Smith of Ga Ga Designs tells PEOPLE. "But I showed (Kim) a $17,000 diamond-encrusted pacifier and she laughed because she's down to earth. They are realistic people. Everything (on the registry) wasn't just the bling bling."
Diddy told the crowd how he found out Porter, with whom he has a son, Christian, 8, was expecting. "It wasn't something that was planned," he said. "Kim and I were sitting down at Nobu and she had told me she was pregnant and I was happy. And she was like, 'That's not it.'
Porter, who is due in the middle of December, teared up when Diddy professed his love for her in front of their friends and family. "I just thank God that I have a woman and a friend who has been down with me with my faults and my flaws and my B.S. and all that stuff," he said. "She's my best friend. I love her with all my heart."
Having girls is going to bring out the rapper's softer side, said Porter, who last week wrapped a new show for MyNetworkTV called Wicked Wicked Games, with Tatum O'Neal.
"I see the way he's been acting," she told PEOPLE.com. "He said, 'I can't wait for them to fall asleep on my chest.' He's going to be very hands on. I don't think he's going to be able to say no to them."