Malcolm in the Middle star revealed what Dewey actor did after show as he is seen for the first time in 18 years

The mystery around what happened to a Malcom in the Middle star has been revealed after the former child actor was spotted in public for the first time in almost two decades.

It's been 25 years since the American TV comedy, Malcom in the Middle, graced our screens in 2000, which boxed off 151 episodes across seven seasons before calling it a day in May, 2006.

And while some of the show's star-studded cast have pursued other TV and movie roles, most notably Breaking Bad star Bryan Cranston, who played Malcom's dad, Hal, in the sitcom, other members of the Wilkerson family have been somewhat less active.

Erik Per Sullivan shot to fame as a child (Jim Spellman/WireImage)

Erik Per Sullivan was only seven-years-old when he first played Dewey, a younger brother of Malcom, played by Frankie Muniz, alongside co-stars Justin Berfield, Christopher Masterson, Jane Kaczmarek and Cranston.

The show followed the four (and later, five) boys as their family expanded and how they navigated their chaotic, dysfunctional teenage life.

But when the show ended, many fans have been left wondering what happened to one of the boys in particular - Sullivan.

As a youngster, he wasn't shy in front of the camera, bagging a starring role in the 2004 movie, Christmas with the Kranks, while playing various other characters in film and TV, including the 2007 movie, Mo, and as the voice of a seahorse in the animated film, Finding Nemo.

The show ran for six years (Fox)

Yet his acting career seemingly came to a sudden end when he was 18-years-old after appearing in the 2010 movie, Twelve, having kept a quiet profile ever since.

That was at least up until recently when the one-time youngest Wilkerson was spotted in Boston amid teasers of a revival of the series on Disney+.

He was seen grabbing a coffee on March 26, with fans remarking from the paparazzi snap just how different the now 33-year-old looks.

Sadly for us fans, the star has decided against the reunion for the new series of Malcom in the Middle, despite the rest of his on-screen family confirming their hotly anticipated return.

Cranston and Kaczmarek are set to reprise their roles as parents Hal and Lois, while Masterson will be back as the eldest son, Francis, along with Berfield as Reese, and Muniz, of course, taking on the role of Malcolm.

Meanwhile, Sullivan, a graduate student studying Victorian Literature, is apparently quite happy to duck out from the chance.

Jane Kaczmarek reflected on the show during an interview (Malcolm France/YouTube)

Kaczmarek previously spoke about his decision to pursue a different career, telling fan site Malcolm France that the star is 'very, very well' but just isn't acting anymore.

"He did Malcolm for seven years, he started at seven, he ended at 14," she said. "He wasn't interested in acting, at all.

"He goes to school at a very prestigious American university that he has asked us all to be quiet about.

"He loves Charles Dickens, he is doing graduate work in Victorian literature."

She added: “I admire it because so many people think being in show business is the greatest thing in the world and it's not for everybody.”

And while many of us are heartbroken over the move, Disney+ confirmed it will recast his role with The Thicket's Caleb Ellsworth-Clark instead.