Jason Mantzoukas may be 52 years old, but on television, two of his most recent longer-running roles have sent him back to middle school and his teenage years. He's currently a fixture on Prime Video's acclaimed superhero animated series Invincible, where he plays the brash demolitions-based hero Rex Splode. Before that, in 2017, he began what has thus far been a seven-season run on Nick Kroll's animated coming-of-age comedy Big Mouth on Netflix as the magic and sex-obsessed Jay Bilzerian. Though the two characters are quite unalike and live in vastly different worlds, there are two aspects that unite them in the actor's eyes—challenge and a lot of growth.

During the premiere of Invincible Season 3, Collider's Nate Richard chatted with Mantzoukas about the journey Rex was on in the Robert Kirkman series, which also brought to mind Jay. Rex comes off in Season 1 as a real jerk, downright antagonizing his would-be teammates, cheating on Atom Eve, and generally displaying immaturity at every turn. As the series progresses, however, it's revealed that he wasn't always that abrasive and, partly thanks to a near-death experience against the Lizard League, he starts making a conscious effort to be better to the people around him, even including Invincible. What Mantzoukas found especially interesting about him and Jay, however, was tackling their growth at completely different ages, as, unlike Rex, Jay is still getting to grips with himself and his sexuality in his early teen years.

When asked if there were any personal lessons he could take away from Rex, Mantzoukas replied "Oh, yeah, sure." However, the challenge of portraying character development from both a hormonal teen and a stunted young adult at the same time in his career has been the most fulfilling part of playing these roles. After seeing Jay float into and out of young relationships, discover his bisexuality, and generally mature, he's having a ton of fun experiencing Rex's own emotional metamorphosis through a different lens. He explained:

"So, you know, it's really what's interesting and hard at the same time. For the last bunch of years, I've been playing a middle schooler in Big Mouth and a teenager, a late teenager on Invincible, as well as various adult characters on other things. So it is funny to try and plug into, if it's Big Mouth, the true chaotic insecurity of middle school age and then Rex Splode. Though Rex Splode is a lot more like he's an adult or he's older, but he has it. His emotional growth is tremendously stunted, you know... the trauma of his childhood and what he and Eve went through. All of that really has created a person who is not closed off to bluff and bluster, not interested in any revealing emotional reality. And what's so fun is to watch that and to be a part of the scripts come in and then performing them to watch that kind of crumble and try and see, like the adult within who's kind of coming to coming out. You know, it's fun to me. Basically, it's fun to help watch this character grow up, you know. It's a blast."

Jason Mantzoukas Thinks Jay and Rex Would Be "Best Friends"

Invincible has on occasion let other IPs bleed into its own world, like in the case of Spider-Man and Batman crossing over in the comics and sort of appearing in the television series. If the kids of Big Mouth and their Hormone Monsters suddenly stumbled into Mark Grayson's world of superpowered beings and ultraviolence, Mantzoukas sees Rex and Jay hitting it off if they got a chance to talk. "Best friends, best friends? Absolutely best friends," he said, citing Rex's powers as a key reason. "Because Jay's super into magic and Rex charges up things. So the two of them together is a gambit."

In Season 3 of Invincible, Rex continues on the path to redemption, according to Mantzoukas, proving once again why we could really use a spin-off to explore his backstory. He's expected to be right in the fray with Invincible and company as they face new threats and prepare to fend off the encroaching Viltrumites. Jay's story isn't over yet, either. Big Mouth's eighth and final season is set to premiere later this year, bringing closure to the series as Nick, Jay, Andrew, Jessi, Missy, and Matthew continue their growth into the next stage of their lives. Although the plot has yet to be revealed, viewers can expect to see everyone continue to adjust to high school, with a battle of the Andrews brewing after Nick makes a new friend at his new school.

The first three episodes of Invincible Season 3 are out now with more coming every Thursday.