Rebecca Romijn & Jerry O’Connell

The first of many playful moments at Rebecca Romijn and Jerry O’Connell’s July 14 nuptials came during the ceremony: As friends and family watched the two exchange vows outside their Calabasas, Calif., home, their dog Better, dressed in a bow tie, moseyed up to his mistress. “He tried to jump into the ceremony!” says a guest. “Rebecca started giggling, and we all laughed as he ran off.”

No stiff formality for this pair. The Ugly Betty star and her groom, whose ABC sitcom Carpoolers begins airing on Tuesday nights this fall, made their invitations by phone (helping their plans stay under wraps), and chose hay bales to seat their 100 guests, among them Romijn’s costars (see box). “It was relaxed, casual and organic—very homespun,” says Vanessa Williams.

A gospel choir sang Foreigner’s “I Want to Know What Love Is” as Romijn, 34, wearing a Ralph Lauren dress and Neil Lane jewelry, approached O’Connell, 33. Their vows were short and sweet—and then the celebrating began. Perrier Jouët champagne flowed as guests dined at picnic tables and waved sparklers. O’Connell serenaded his bride with Williams’s hit “Save the Best for Last”—before Williams stepped in, belting out the final verse herself. Undeterred, the groom “did the same with a Fergie song,” says Ana Ortiz. But Fergie, who was on hand, “was like, ‘I’ll sing it!'” Ortiz continues. “We got a little private concert.”

Dancing under the stars to tunes spun by DJ Dave Meek continued until past midnight, and there were flip-flops on hand for tired feet. “It was lovely,” says America Ferrera. “The most fun ever,” declares Ortiz. Says Romijn: “It was the perfect celebration. Jerry and I couldn’t be happier.”