In case you were wondering...

Pre-Saved by the Bell Mario Lopez was on the Golden Girls in 1987 in the episode "Dorothy's Favorite Pupil". He plays a 12 year old kid named, funnily enough, Mario Sanchez, who gets deported to Mexico.

Pre-ER George Clooney is featured two episodes later, in "To Catch a Neighbor". He plays a cop and has 7 lines. He has since undergone extensive orthodontia. He was still a dreamboat.