'Jimmy Neutron' Star Jeff Garcia Dead at 50

Jeff Garcia -- the beloved voice actor who appeared on many popular 2000s shows -- has died ... TMZ has learned.

Multiple family members tell TMZ ... the comedian and actor was pronounced dead early Wednesday morning after he was taken off life support Tuesday night at a Southern California hospital while surrounded by family and friends.

We're told Jeff was dealing with multiple medical complications in the months before his death ... suffering a brain aneurysm back in the spring, during which he fell and hit his head. He recovered from the aneurysm, but our sources say he suffered a stroke several weeks ago.

Our sources say Jeff canceled multiple shows recently because he wasn't feeling well ... which wasn't like him at all, but he didn't go to the hospital, believing he'd be fine without treatment.

We broke the story … sources told us Jeff had previously been hospitalized around November 20 with pneumonia. He recovered enough to be discharged, but his health took another turn in recent weeks. On Monday, he went to the hospital with difficulty breathing and on Tuesday, his lung collapsed.

Jeff might not be a household name, but his voice will certainly be familiar to many ... with the actor first grabbing notice with his iconic voiceover work in the “Jimmy Neutron” franchise -- bringing fan-favorite Sheen Estevez to life in the 2001 film “Jimmy Neutron: Boy Genius” and in 59 episodes of “The Adventures of Jimmy Neutron: Boy Genius.”

Sheen proved so popular, Garcia starred in his own-spinoff show titled "Planet Sheen" ... which ran for 26 episodes beginning in 2010.

Among his other credits ... the movie "Barnyard" and its accompanying TV series "Back at the Barnyard"; both "Happy Feet" movies; "Marmaduke"; both "Rio" movies; and the live-action sitcom "Mr. Box Office," just to name a few.

Jamie Masada, Laugh Factory owner, tells TMZ ... Jeff was a special comedian ... 'cause he had a huge heart and used his success for outreach to the Latino community, helping to inspire young comics. He added ... "Jeff's a comedian who needs to be remembered." Shortly after news broke that Jeff passed, Jamie had the Laugh Factory post a tribute on the iconic Hollywood marquee.

We caught up with Jeff back in 2012 ... and he wasn't afraid to weigh in on Ashton Kutcher's shocking Popchips brownface commercial.

Outside the film and TV world, Jeff built a career as a standup comic … performing regularly and even appearing onstage in early November, just weeks before his hospitalization.

Jeff was 50.