Kirstie Alley Reunites with 'Cheers' Cast Mates to Celebrate Maintaining 50-Lb. Weight Loss

Kirstie Alley stars in a new Jenny Craig commercial with John Ratzenberger and George Wendt

Kirstie Alley is going back to where everybody knows her name.

The actress, 64, lost 50 lbs. with Jenny Craig and has kept off the weight for the past year – and now she’s celebrating her success with some familiar faces in a Cheers-themed commercial for the diet program.

“When they asked me to do the commercial, I had a lot of consideration that it was an iconic show – I didn’t want to walk onto some set that looks artificial,” Alley tells PEOPLE.

But her fears were put to rest when she saw the set, which perfectly recreated the bar from the popular 80s sitcom.

“Honestly, when John [Ratzenberger] and George [ Wendt] and I walked on, it was a little bit like The Twilight Zone because it was an exact duplicate,” she says. “It was crazy. I didn’t think anybody would ever be able to replicate that set like that.”

Reuniting with her old costars, was “so much fun,” says Alley.

“We were immediately joking around, making fun of everything in the universe – mostly ourselves,” she says. “When I’m around those guys, we just revert to basically exactly how we were when we were doing the show.”

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The star even joked on Today, Tuesday, that the bit made her think “why don’t we do just do [the show] again?”

Alley shows off her svelte figure in the new ad, and gives Jenny Craig full credit.

“The thing [about Jenny Craig] that works best for me – other than really awesome yummy food, because it really is the best – is that you have a consultant,” she tells PEOPLE. “Going in every week and weighing in makes you accountable. I’m doing maintenance now, so I only weigh in once every four weeks, but that accountability for someone like me is vital!”

Alley also loves that she can still eat foods that feel indulgent while sticking to her diet plan.

“My favorite food remains chicken fettuccini, and then they have this new dessert, which is chocolate lava cake,” she says. “You’re supposed to pop it in the oven, but I eat it right out of the freezer! I like it like that. It’s dense and yummy.”

While Alley famously gained weight after ending her role as spokesperson for Jenny Craig in 2007, she’s happy she’s back with the program, and is encouraging anyone else who has yo-yoed in the past to get back on track too.

“I think when people lose weight and the weight comes back on them, they get sort of embarrassed, and they maybe are hesitant to come back to something, but I just came back to what had been successful for me,” she says. “I would just say, ‘Come on back, come on home. Don’t be embarrassed. It happens to the best of us!’ “