'How I Met Your Mother' Season 9: Co-creator Carter Bays on the 'liberating' final season, time travel and ... the pineapple?

cristin-milioti-how-i-met-your-mother-season-8-finale.jpgWhen CBS announced that Season 9 of "How I Met Your Mother" would be its last one, and that it would unfold entirely over the course of Robin ( Cobie Smulders) and Barney's ( Neil Patrick Harris) wedding weekend, the reaction was ... mixed.

Would fans who waited eight years to see Ted's ( Josh Radnor) future wife ( Cristin Milioti) have to wait another entire season to see him finally encounter her face-to-face, all in service of a wedding the show has teased for the better part of two years? At first blush, it seemed like a grand exercise in delaying the inevitable.

"The whole 'it's going to be the weekend before the wedding' thing, I get the reaction," co-creator Carter Bays tells Zap2it. "If you haven't been in the writers' room with us cooking it up and you just hear that, you'd think 'They're just pushing back the end-zone line.'"

He hopes, however, that skepticks will change their mind after seeing the start of the season. In a recent interview, Bays explained the structure of the final season, the secrecy surrounding Milioti's casting and some other issues "HIMYM" will cover in its final run.

Zap2it: What was the timeline of deciding this was the final season? Was it getting the renewal and then deciding the structure?
Carter Bays: A lot of the decisions came out of necessity, but a lot of them were things that became opportunities. I think the 56-hour issue was the big one. We definitely felt like, for various reasons -- the ages of [Ted's] kids and things -- Barney and Robin had to get married in May 2013. That was the thing we were stumbling on, and then [co-creator] Craig [Thomas] had the idea of, What if we did a whole season just over the course of the wedding, but use that framework as a springboard to tell stories from 10 years in the future, 10 years in the past, stories at the wedding? Because there are certainly lots of stories to come out of that.

We had that idea around the time when we were trying to decide, "Do we feel like we have another season in us?," which was last fall. I think we were in talks with the actors, but we didn't have a deal. We were ready to squelch it right away if we felt like we only had 13 episodes left in us. But then this idea came up, and more ideas came snowballing out of that. It became such a big idea that it definitely at a certain point, it tipped the scales. It made it feel like if we don't get to do this ninth season, we're going to regret it for the rest of our lives.

I have to say I was skeptical hearing about the format at first. How much of the season is set in the show's present, and how much jumping back and forth do you do?
I think the thing that keeps fuel in our tank is having something new to write. We don't want to write the same thing over and over. At that point we were actually sort of surprised by some of the reactions, because ... just from our standpoint, coming into work every day, we're writing stuff we wouldn't have written any other season. It's giving us a lot of new material. Meeting the mother was also the big puzzle piece in this, because we get to tell all the stories about her we want to tell. We get to get to know her and explore that part of the show. At one point we were never going to meet her -- there was a point when it was just, you meet her in the last scene, and after nine years, it felt like you deserved more.

My hope had been that there would be a season where Ted and the mother are together, so we get a sense of why she was worth such a long story. Does the plan you have kind of allow for that?
Without giving anything away, we felt the same thing, and we wouldn't have devised this season if we weren't planning on seeing that in some way. I wouldn't want to give it away, because it's a fun device, the way that we explore her life. But yeah -- the whole "it's going to be the weekend before the wedding" thing, I get the reaction. If you haven't been in the writers' room with us cooking it up and you just hear that, you'd think "They're just pushing back the end-zone line." [Like] we're just waiting and it's going to be 23 episodes of spinning our wheels. I think it will be clear in the first two episodes -- we're getting to write stuff that we haven't been able to write and have been wanting to write for many years now.

In terms of guest stars, is there anyone else you think needs to come back?
There are so many people we've loved having on the series. The more we look at our casting list for this season, the shorter list is the people who don't come back. Because by nature of this season, it's really all over the map time-wise. You're seeing things from 10 years ago, from five years ago, two years ago, two years in the future, 10 years in the future. This story is a very sprawling, epic story.

So it's sort of like your Season 5 of "Lost"?
I guess so, yeah. There is absolutely time travel in this season. It's fun. This season, much more than in previous seasons, says the things we've always tried to say on the show about memory and about storytelling -- the order in which you tell stories, the way you remember things. We're getting to say a lot. There's a feeling on the staff of leaving it all on the field. Craig and I are probably going to be in hospital beds by the end of the season. But we'll be happy -- we'll have smiles on our faces.

Has much changed from your original idea of the final chapter to what you're doing now?
The one thing that has changed is meeting the mother. That's been the biggest change, and ... that's the element in the story where we threw away the plan, and it was really liberating. Now it's kind of wide open, and we're getting to tell stories we never imagined we would tell. It helps having Cristin Milioti as the mother, who's just so fantastic. She's just a brilliant performer. She only had one line last year, so it's kind of hard to tell, but she's great. It's going to be her season as much as anyone else's.

What was the discussion like when you decided to cast the mother?
Honestly, I don't think we said OK until we settled on Cristin. Craig and I kind of did our due diligence and said if we're really going to do this, it has to be the right person. We did our due diligence in writing up audition sides, and we brought her in to do a chemistry test with Josh. She was the first person that our casting director, Marisa Ross, suggested. Her instincts are always dead on, and I know she had her little secret file of potential mothers going, just in case ... and Cristin was at the top of the list.

We brought her in and did the chemistry read, and it was like -- I wish we could broadcast it, it was so good. It was just terrific. She and Josh were so great together. It'll be on the DVD, for sure. It's really cool. It was also exciting -- I'll say, it was the meeting. We wrote the meeting scene. In that moment, we kind of knew: OK, this feels right. We need to do this, we need another season so we can tell the story.

How did you keep it such a secret? Were the audition sides not related to the show at all?
We had an audition -- I wish I could remember the name of the script. We wrote this really douchey title for something that was like -- we called it "USC senior thesis film." We made sure it was a script that if someone found it on a bus, there was no way they'd want to read it. That was the script, and the level of security was really fun. It really felt like we were pulling off Watergate. All the extras you see in that train station [scene where Milioti makes her appearance] were staff members of the show -- the writers and the assistants from the office. We were very, very careful.

Going back and forth in time probably gives you more leeway to get Marshall's [Jason Segel] last two slaps in, right?
We have a gloriously stupid episode planned for the final slap. It's just marinating -- I can feel it. ... It's going to be just so delightfully dumb. It's everything we love to do, and it's a nice break from -- there's a lot of high drama this season. A lot of big s*** is going down. But in the middle of it somewhere is this slap episode that's so much fun and so silly and stupid.

What was the cast's reaction when you laid out the plan for the final season?
I think they were excited. We kept it quiet for the most part. Some people know more than others -- I can't really elaborate on that without giving anything away. But they're going into this -- at least two of them are going into the season with a big secret, and there are probably more secrets that are going to come out that we don't know about. But they're excited -- they try to know as little as possible so they can be surprised and play it well.

Does knowing this is the last year change the way you break stories? Can you back-fill from the end point now?
It has everything to do with how we write the season. We've charted [it] out, we know every episode of the season right now -- it's just a matter of filling in the gaps. But it's been great. The fact that we can write about the mother, that was one of the reasons we wanted a ninth season. The other one was, this way we know how many episodes to have to get this done. It's easy to plan.

So everything but the pineapple is going in?
Everything but the pineapple. And just to say this cryptically, someday we'll find out about the pineapple. It might be long after the show is over, but someday we will find out about the pineapple.

Season 9 of "How I Met Your Mother" premieres at 8 p.m. ET Monday, Sept. 23 on CBS.
Photo/Video credit: CBS