'How I Met Your Mother' Creators Share 6 Plans for the (Possibly Final) Season 8

How I Met Your Mother Farhampton - H 2012
Monty Brinton/CBS

How I Met Your Mother Farhampton - H 2012

When How I Met Your Mother returns to CBS on Sept. 25, it could be the last season premiere the veteran comedy will ever air. It could also be the first of 40-plus more episodes.

The network, 20th Century Fox TV and the cast are currently in talks to renew the show through a ninth and final season, but when co-creators and showrunners Carter Bays and Craig Thomas met with a few reporters a week ahead of their show's return, they said they're still proceeding as if it's the last.

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And with the final season of a comedy as complicated and steeped in its own serial folklore as How I Met Your Mother, there will be a lot of big developments. After screening the upcoming premiere, "Farhampton," The Hollywood Reporter learned several key plans for the upcoming run. Needless to say, spoilers follow:

It's the beginning of the end: "I think I can say that the premiere is the first episode of the last season of How I Met Your Mother," says Thomas. "I don't feel like we altered it because of not knowing if it's the end. We're writing this season like it's the end. We'll have to have a Plan A and a Plan B going, and we're approaching the moment where those plans diverge." The duo also think they'll know relatively soon which course they need to take. "It gets more and more difficult as it goes on," added Bays. "We'd like to know as soon as possible, but it's a lot of big machinery moving around."

Sweeps is the breakup month: The season picks up with several happy unions -- Barney (Neil Patrick Harris) and Quinn (Becki Newton), Ted (Josh Radnor) and Victoria (Ashley Williams), Robin (Cobie Smulders) and Nick (Michael Trucco) -- but none of them will stay that way. "We've shown you the end of these relationships," Thomas says. "We know that Ted doesn't marry Victoria, and we know that Barney doesn't marry Quinn. We're just sort of having to show you the path of carnage that ends these relationships. All three of these breakups will be different. That's the goal of breakup month, to show you three different dissolution of relationships.

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Robin and Barney will reunite soon: Flashing forward to their wedding in last season's finale, the endgame for the series' on-again/off-again couple is finally set. And they'll start down the road to the long-awaited nuptials very soon. "I think we've come up with a fun, weirdly appropriate way to get them back together," Thomas hints.

Marshall (Jason Segel) and Lily's (Alyson Hannigan) baby won't be forgotten: "I'd like to think that we are tending to the fact that they have a baby more than other shows have," says Thomas, "but the baby doesn't take over the show." The baby has altered production though. Bays and Thomas say that the addition of the babies -- Marvin is played by twins -- has been really demanding on set, but they are good little actors. "Honestly, they're giving us better reactions than some of our main cast."

Joe Mangienallo's return: The True Blood star, who last appeared as Marshall's law school buddy Brad in 2009, is back for several episodes in November. "It will be Marshall's biggest trial that he's ever had and Joe is involved," says Thomas. "We set it up last year, with Martin Short's firm." The trial will also include the arrival of guest star Joe Lo Truglio, who'll play Short's previously unseen partner in the firm.

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Bringing back old guest stars: If this really is the end of How I Met Your Mother, the creators want the show to pay homage to as much of their legion of past guest stars as possible as they approach the finale. "We have a plan to bring back many people we've had on the show," says Bays. "Not to steal their idea, but I loved the Seinfeld finale where you saw everyone that's ever that's been on the show. We have a way to do it that sort of fits in with the universe of our show. Hopefully there will be a cavalcade of familiar faces."

How I Met Your Mother returns Sept. 25 at 8 p.m.