Jerry Seinfeld Cast Jon Hamm and John Slattery as Ad Execs in Unfrosted So He Could 'Finally Be in Mad Men'

Jerry Seinfeld took the chance to fulfill one of his life goals when directing his new Netflix comedy Unfrosted.

The comedian, 70, always dreamed of being on the hit AMC series Mad Men, which had a seven-season run from 2007 to 2015. So when casting Unfrosted, he asked the show's stars, Jon Hamm and John Slattery, to play advertising executives in his film about the creation of Pop-Tarts.

"A reason I made the movie is because I couldn't be in Mad Men, but I thought I could be in a suit in the '60s in an office, so it was as close as I could get," he tells PEOPLE.

The film takes place in the same era as Mad Men and Hamm and Slattery play ad execs similar to their Don Draper and Roger Sterling characters.

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Besides Hamm and Slattery, the comedy features an ensemble cast including Melissa McCarthy, Jim Gaffigan, Hugh Grant, Amy Schumer, Max Greenfield, Christian Slater, Bill Burr, Daniel Levy, James Marsden, Jack McBrayer, Thomas Lennon, Bobby Moynihan, Adrian Martinez, Sarah Cooper and Fred Armisen. And Seinfeld says working with the cast was the highlight of making the film.

"Amy was very reluctant to play a villain. She'd never played a villain, and I said, 'You'll be a great villain.' And she was great," says Seinfeld. "And Melissa is unbelievably funny and came up with all those crazy outfits and hairdos. I just said, 'We're just going to have fun with this.' "

But doing the Mad Men-type scene with Hamm and Slattery is something he will never forget.

"When Jon and John agreed I thought, 'Oh my God, I'm going to be in Mad Men finally!' " he says. "That was a dream come true."

For more on Jerry Seinfeld, pick up this week's issue of PEOPLE on newsstands Friday.