Mario Lopez and Elizabeth Berkley in Character For 'Saved By The Bell'

Mario Lopez and Elizabeth Berkley are back on campus for another round of "Saved By The Bell" ... which means they're back in character as A.C. Slater and Jessie Spano.

Mario and Elizabeth were spotted shooting the reboot Monday in Los Angeles, over 30 years after they first started starring in the hit series way back in 1989 ... talk about a blast from the past.

Mario doesn't look like he's aged much at all ... and he's still got those famous A.C. jock vibes. Elizabeth's keeping it business casual as Jessie ... the former students are reportedly playing roles as parents in the reboot.

Bayside High School is where it's all going down once again.

The new series is said to focus on a group of low-income students transferring into the wealthy Pacific Palisades at the direction of Zack Morris, who went on to become Governor of California.