09/05/2007 at 04:00 PM EDT
He may not be getting much sleep, but Patrick Dempsey
is having fun with fatherhood and filming Season 4 of Grey's Anatomy
The actor tells Extra
that his 6-month-old twin sons
"are developing beautifully ... It's a lot of fun."
It's a sentiment he echoes when asked about filming the latest installment of his hit TV show: "It's a lot lighter, people are having more fun."
"The energy and the adjustments make a big difference," he says, referring to the departure of Isaiah Washington after an on-set altercation
between the stars last season.
Definitely pumped to be back at Seattle Grace, he declares, "I'm going to go save some lives again!"
Dempsey, 41, who races
cars on the Hyper Sport racing team, plans to have twins
Darby Galen and Sullivan Patrick driving "soon enough."
"You can get those little go carts," he says, but there'll be "no pressure" for them to race like dad.