Tyler Baltierra Admits He and Catelynn Lowell First Signed Up for 16 & Pregnant as a 'Joke' (Exclusive)

Catelynn Lowell and Tyler Baltierra never thought much about life outside of their small town.

That all changed when what started as a joke turned into the beginning of their journey on reality TV, the couple tells PEOPLE while celebrating a special Sweet 16 episode of Teen Mom: The Next Chapter, commemorating the original crop of 16 & Pregnant kids turning 16 themselves.

"I think for us in the very beginning, going back to filling out paperwork to even see if we'd get picked, we thought for sure like, 'There's no way in hell they're going to pick a little tiny couple from the little town of Marine City, Michigan. Nothing ever happens there,' " Catelynn tells PEOPLE.

"So Tyler just filled it all out," she continues, before Tyler admits, "I did it as a joke."

"We didn't think... we definitely didn't think we were going to get picked. But why not fill it out? So then we got the call that we were chosen, which was so weird. At our age growing up, MTV was True Life and waiting for music videos to drop. It was our channel. Then to find out they wanted to follow our adoption journey, we were like, 'Oh my gosh, this is absolutely crazy.'"

They continued their journey on Teen Mom, which required "convincing our families to allow us to participate, because we were minors."

"Tyler's mom and my mom had to sign for us to film," Catelynn says. "There was lots of talk, lots of convincing. And we thought we would be on like an episode or two of something, because we had no idea what it would become."

Once the episode came out on July 16, 2009, the two remember, "It was everywhere."

"Back then, it was a lot more magazines. There were magazine articles about us and when we were grocery shopping, we saw our face on the cover of a magazine," Tyler recalls. "We were like, 'This is really weird now.'"

"At that age, I don't think you really grasp what is really going on. Because I feel like since our show is such a docuseries anyway, it's like, 'I'm just literally living my life and people are watching it.'"

Sharing the complex feelings that came after daughter Carly's adoption in May 2009 wasn't always easy, but Tyler is proud of speaking and showing their truth and how the decision made 16 years ago continues to impact them today.

"Honestly, I feel like it was the first time that really adoption has ever been shown in a true light. Before that, we had Juno, which was over-exaggerated; we had Lifetime movies, which were over-exaggerated. There was never a real, solid, concrete, truthful documentary of an adoption happening, especially an open adoption," he explains.

"So I think that alone just broke a lot of feelings and got people talking, and it brought adoption into the conversation, into people's houses that may not have talked about it before."

"I feel like looking back, it was really hard, but I feel very honored that we were a small part of that kind of bigger discussion happening," he continues. "Because now that adoption is documented and even the aftermath of that adoption is documented. We never got to see that before our story. So it's honorable in my opinion."

Catelynn adds, "For me, just sharing everything that we have shared, I get messages all the time of people stating that talking about my miscarriage or my mental health journey really helped. I feel like that's a huge driving force for Ty and I, is that if our story is making an impact — even if it's just in one person's life, that's important."