This director made a joke about adoption. What followed became the basis of a new film.

Sean Anders never expected that an off-hand joke would change his life.

The writer and director (who's responsible for comedies like "Hot Tub Time Machine" and "She's Out Of My League") and his wife, Beth, had been discussing the possibility of having kids when he joked that he might be too old to be a dad.

"Why don't we just adopt a five year old? It'll be like I got started five years ago," Sean recalls saying. "I was totally kidding, but she took it seriously enough to get us moving down the road."

The couple began doing research and quickly realized something important — while there were many kids looking for their forever families, older children had a much harder time being adopted out of the foster system. Suddenly, Anders' joke about adopting a five-year-old started to become more real.

"Once we decided to move forward, it was scary and overwhelming, but we were very open to whatever came our way," Beth says.

Adopting kids is a huge decision. So they decided that their best option was not to decide, orat least, not right off the bat.

The couple connected with The Seneca Family of Agencies in California to begin the process, but they both agreed that they wouldn't jump into anything hastily.

"We decided that we would just go to the orientation, and we wouldn't decide," Sean says. "When we found out that we had [to take] classes, we just thought, 'Well, let's just take the classes and see what happens.'"

What ended up happening was that the Anderses, who had only been considering adopting one child, adopted three.

In 2012, they became the parents of an 18-month-old, a three-year-old, and a six year-old — a trio of siblings who'd been removed from their mother due to her dependence on drugs.  

The next few months were some of the hardest of The Anderses' lives. They'd been confident that they'd be able to handle the challenge of creating a family overnight, but quickly realized that they might be in a little over their heads.

"We would lie in bed at night and just try to figure out some way that we could get them out of our house," Seam wrote in a piece for Time. "They were completely ruining all of our fun. When you get three at once you don’t have time to get your sea legs. It was kind of like babysitting someone else’s kids, but forever."

However, with a bit (okay, a lot) of adjustment, the family is now a complete unit. Sean and Beth wouldn't trade their kids for the world.

They're also correcting some major misconceptions about adoption while they're at it.

One of those misconceptions is that adoptive parents fall in love with their kids right away, and vice-versa.

"I think most people, they need to build up that trust and that love between them," explains Sean.

But that trust and love does build up through hundreds of tiny gestures every day, and eventually the feeling of belonging overwhelms everything else. For Sean, there was a specific moment when he realized that his family was no longer two adults and their three adoptive kids but one complete unit. It came after months of messes, and arguments and sleepless nights.

"There was this one day that I woke up, I think it was a Sunday, and it was in the morning, and it was very quiet in the house. My wife was still asleep, and the kids were still asleep, miraculously. I had this strange feeling in my gut that I couldn't quite identify. Then I realized that, I thought, oh man, I miss them right now. I'm excited for them to come running in to my room and wake us up. I knew in that moment that I had fallen in love with my kids."

If this story sounds a lot like trailers you've seen for the film "Instant Family," it's because the movie is based on The Anderses' experience. Sean's hope is that it gives people an honest look at what adopting kids can really feel like.

Often adoption stories focus on the difficulty of the process, but that's not all there is to it.

While they were growing into their new family, the Anderses definitely felt some heartbreak, but there was a lot of laughter, too.  That's ultimately why Sean decided to make "Instant Family."

His hope is that audiences leave the film with a clearer, more compassionate understanding of foster youth, and that they recognize how rewarding adoption can be for everyone involved.

"I just want [audiences] to walk away having a better idea of who these kids are," he says.  "And that, when they hear the word foster care, it doesn't automatically conjure feelings of fear, and pity and anxiety; but instead, conjures lots of compassion and love, and even enthusiasm, because...these kids, they're just kids. And they need us. And we need them."

“Hopefully you realize that they’re just family," he says of the characters on screen. "That could even be you. That could be your kids and your family.”

To learn more about The Anderses' journey and "Instant Family," check out the video below.