Alyson Hannigan Reveals 'American Reunion,' Details, Talks 'How I Met Your Mother'

Alyson Hannigan grew up in Hollywood. And Hollywood has grown up with her.

The gentle, always smiling actress made her commercial debut as a child, starred in "Buffy The Vampire Slayer" and then shot to true stardom as the awkward, flute-loving prom date to Jason Biggs' pie-loving character in the first "American Pie" film.

Each subsequent sequel of the dessert defiling series brought the awkward crew to a new stage in their lives, from high school to college to, in 2003, marriage. It's become a generation-defining trilogy, and to hear Hannigan tell it, a total surprise, too.

"With the first one, they had put some sort of sequel clause in my contract and I was like, 'ahh, I wouldn't be in a sequel,'" she laughed in a conversation with The Huffington Post. "'There's no way. My character leaves at the end of the movie, so even if there was a sequel, I wouldn't be in it.' And here we are."

Where Hannigan is, exactly, is Atlanta, filming "American Reunion." Thirteen years after Jim and co. pledged to lose their virginity, their high school reunion brings them all back together. And as unlikely as it seems that the kid who crotch dived into a pie is the father of perky band girl's child, that progeny is a major player in the new film. Continuing the pattern, Hannigan has a child now, too.

"I haven't met my child yet for the film but I'll meet him today, I hope he likes me and I hope my daughter doesn't get jealous that I'm holding some other kid. I'll have some explaining to do," she laughed. "Like, 'why is that kid calling you mommy?' I don't know how old the actor kid is, but he's playing two, and my daughter's two, so they're probably in the same ballpark. I'm hoping they're in the same weight category, because I'm only just holding my daughter who is 25 pounds, if he's much heavier, I could struggle."

Which, of course, would actually be pretty funny.

Beyond the child, though, there are many old cast members to catch up with. If you've imagined what crazy paths Stiffler, Finch, Jim and the gang may have taken, you may just see them on the big screen. And that real life awkwardness at high school reunions? Not in this one.

"It's really true to how real life would be, where everybody, they've all gone in different directions, but of course when you get back together again, it's as if no time has passed," Hannigan said. "You'll be able to catch up with all the characters, see what they're doing, where are they now, it's as if no time has passed when they all come back together. It's my second day of shooting, but already it's been such a blast and I can tell it's going to be really, really funny."

It's not just the characters who jump right back into it -- having gone through such a big, star-making experience so young, the actress, now 36, says that there's a sort of friends-for-live vibe on set that matches their characters.

"It's fantastic. There's such a fantastic chemistry among this group and it certainly has not diminished at all," she offered (as if to prove it, Jason Biggs was goofing off in the hair and makeup trailer during the interview, plugging his just-cancelled show, "Mad Love," which he'd love to bring back, if anyone is interested). "If anything I think it has sort of gotten better because we all have this sort of common thread of here is this little movie that became this gigantic franchise, so it's been really, really fun to be a part of."

For Hannigan, motherhood is becoming a constant theme, both in life and on screen. Beyond her own child, and her child in "American Reunion," her character in "How I Met Your Mother," became pregnant at the end of this last season. She's especially excited to see how that plays out on the screen -- and to see what the baby will look like. Carrying this one will definitely be a problem, though, if it's anything close to what she imagines.

"It'll probably be a lot like, remember in 'Mork & Mindy' and the kid aged backwards from a man?" Hannigan mused. "That's what I picture. Just because, if the baby has Marshall's genes, he'll probably come out 5 foot 6."

With all this pregnancy and baby talk, perhaps it's fitting that Hannigan is supporting the March of Dimes, the great pregnancy charity resource for expecting mothers.

"It's so easy for people to make a difference and to donate money to the March of Dimes," she said, discussing their new fundraising campaign. "For every person that goes on to the Johnson's Baby Facebook page and hits like, for every like they get, they're going to donate a dollar to March of Dimes. It'll take a minute, it's such a great cause, and it's an easy way for people to make a difference."

For all her obvious maturity, though Hannigan still has a soft spot for the Muppets, a franchise which, conveniently, is being re-invigorated by her "How I Met Your Mother" co-star Jason Segel.

"I'm so so happy. I keep thanking him for bringing them back. And I got to take my daughter to set when he was shooting. And she doesn't watch television or anything, but she got to see Ms. Piggy and one of the other Muppets, and you could see the magic in her eyes," Hannigan lit up. "She still to this day talks about Ms. Piggy and she was so happy and it was such an experience, even having never seen or heard about the Muppets, she got how special they are, so I keep thanking him for that experience for me and my daughter."

On-screen and off, Hannigan has settled into the unlikely role of cool mom. "I like how my career sort of mirrors my life, because in the last 'American Pie' film, it was 'American Wedding,' and I was actually planning my wedding," she said. "And now we're doing this, and I have a two year old and Michelle has a two year old. So I'm just keeping on track."