'Malcolm in the Middle' Erik Per Sullivan Spotted for First Time in 18 Years

Erik Per Sullivan used to be on TV all the time as a star on the hit 2000s sitcom "Malcolm In The Middle" ... but he vanished from Hollywood for nearly two decades, and now he's finally been spotted in his new life.

The seemingly retired actor played Dewey Wilkerson on 'Malcolm' ... and while he still looks a little like his TV character, the guy's done some serious growing up in 18 years away from the spotlight.

Erik was spotted last week in Boston, grabbing coffee and running some errands ... the first time paparazzi has snapped him since 2007!!!

While it's extremely rare to see Erik, the timing here is not completely random ... 'Malcolm' is getting a reboot and he's the only main character who is NOT returning.

Frankie Muniz, Jane Kaczmarek and Bryan Cranston are all reprising their roles ... but not Erik. He left Hollywood back almost two decades ago, reportedly to begin a career in education.