Rare video of Erik Per Sullivan is last known footage of child star before he disappeared from public eye

Malcolm in the Middle fans were delighted last week after a paparazzi snap of former child Erik Per Sullivan went viral online.

The heartwarming image marked the first time that the actor has been seen in public in over 18 years.

In the photo, Sullivan - now 33 - bears a wide smile during a day out in Boston. He can be seen donning a thick jumper, a pair of green trousers and boots whilst carrying some shopping bags in his arms.

Following the photo release, fans of the nostalgic family sitcom seemingly began frantically searching for the last known footage of Sullivan.

And in doing so, they've managed to dig up an undated clip of the star, where he appears to be a teenager.

Check out the footage here:

"Hey [ - ] my name's Erik Per Sullivan and I just thought I'd say hi spontaneously because your uncle did not encourage us at all, he's a good guy," the actor says in the clip.

"Yeah I heard you liked the show and I'm just sending greetings from where ever we are... pause the time."

The video appears to have been recorded when the actor was a teen - around the time he gained his last acting credit for the 2010 teen crime-drama Twelve, in which he appeared when he was just 18.

For those in need of a reminder of Sullivan's most recognised work, the youngster first shot to fame all the way back in the year 2000, after being cast in the FOX family series, Malcolm in the Middle.

He appeared in the role of 'Dewey' on the show for six years alongside his on-screen brothers Frankie Muniz (who played the titular character), Christopher Kennedy Masterson and Justin Berfield (Francis and Reese).

The actor quit acting not long after the show (Jim Spellman/WireImage)

Equal Justice actress Jane Kaczmarek and Breaking Bad front-man Bryan Cranston also starred as the trio's parents, Lois and Hal.

In the years following the conclusion of the hit series, however, Sullivan shied away from appearances at cast reunions.

And when a reboot of the series was announced earlier this year - involving his five co-stars - producers disclosed that Fargo actor Caleb Ellsworth-Clark would be taking over as 'Dewey' - as per Variety.

Naturally, therefore, fans of the show were pleased to see Sullivan happy and healthy this week in his new snap.

One gushed on social media: "He’s looking great! Hope he is happy and doing well!"

"Hope he’s living his best life out there," another added.

Sullivan's TV mother Kaczmarek previously told press that following the success of the sitcom, the actor turned his attention towards education.

Now, he is understood to have attended university, and is reportedly studying Victorian Literature as a graduate student.

His last known film credit was 2010 (Sylvain Gaboury/FilmMagic)

During an appearance at the Paris Manga Sci-Fi Show last year, Kaczmarek explained: "He’s very very well.

"He did Malcolm for seven years. He started at 7, he ended at 14. He wasn’t interested in acting at all."