Rebecca Romijn and Jerry O'Connell
Jean Baptiste Lacroix/WireImage
and Jerry O'Connell's twins may only be 5 months old, but their personalities are starting to show through – especially their sense of humor.
"They're really developing their own, very specific personas," the Ugly Betty
star told PEOPLE at the Dior Beauty Luncheon Wednesday at the Shangri-La Hotel in Santa Monica. "They're starting to think that things are hilarious, like they're noticing the dogs as being anything other than furniture. The dogs were play-fighting the other day and they thought that was hysterical."
Romijn's three pooches – Taco, Better, and Bim – aren't the only things the girls, Dolly Rebecca Rose and Charlie Tamara Tulip, giggle at. The parents' bowling skills are apparently laughable as well.
"Jerry and I went bowling last weekend and we put them in their infant seats right in the front so that they could watch us, and they thought it was hilarious," she said. "It probably was. They were laughing at my score. Like, 'Mommy can't knock down any! It's so funny!' "
The twins, who were born in December
, are the first children for Romijn, 36, and O'Connell, 34. And Romijn is no stranger to the exhaustion that being a new mom brings.
"Sometimes I'm so tired, I look down at what I'm wearing, and if it's comfortable enough to sleep in, I don't even make it into my pajamas," said the actress. "I'm looking down, and I'm like, 'T-shirt and stretchy pants? Yup, that's fine. It's pajama-y, good night. Sorry, Jerry!' "