Jon Hamm: Billionaires Feuding Kept 'Mad Men' Off the Air

After a long absence, Mad Men finally returns for a fifth season on March 25 -- a date that is doubtless marked in the calendars of the show's superfans as they wait with anticipation over what happens next in the messy, sophisticated saga of Don Draper and company.

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In a guest appearance on Thursday's Letterman, Jon Hamm -- back on the promotional circuit for the AMC series -- blames billionaire-on-billionaire squabbles for the 17-month delay. (The season-four finale aired in October 2010.)

"These decisions get made ... at a much higher pay grade than I'm allowed to partake in," Hamm explained on CBS' Late Show. "I've described it thusly, and I've gotten in trouble, so I'll do it again the same way: when billionaires fight, it takes a lot longer to, like, settle. So we had some very wealthy people determining how long we would be off the air."

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Mad Men is "finished with production," said Hamm, adding: "Season five is in the books."

Series creator Matthew Weiner teased the new installment in a recent interview with THR.

"The year doesn’t really mean anything,” Weiner said of the '60-set drama. "It doesn't. I'm not doing a history lesson. The thing that I'm excited about is I wanted to give people a big helping. I wanted a two-hour premiere. It’s a Mad Men movie -- I don't think anyone's going to think it’s two episodes spliced together. There is a story that starts in the middle of it (but otherwise) it's one story. The beginning and the ending are related to each other."

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The premiere, written by Weiner and directed by Jennifer Getzinger, will kick off that Sunday at 9 p.m. The following week's episode, returning to its regular 10 p.m. timeslot, marks the Hamm's directorial debut.