"I was always used to playing off of her and looking into her eyes," Diamond says of his former costar. "When I saw her at the commentary, it wasn't the Lark I knew."
Voorhies stared into space, Diamond says, much like she did during a series of interviews with PEOPLE. Voorhies says she is spiritual, but her mother Tricia revealed her daughter was diagnosed with bipolar disorder.
She wasn't always like this. Voorhies, who famously played the bubbly Lisa Turtle on the '90s Saturday morning sitcom, was just as engaging offscreen, recalls Mario Lopez.
"[She] came from a real nice family – close with her mom. She carried herself like a little lady," says Lopez, who played jock A.C. Slater on the show. "She was a sweet, pretty, cool teenaged girl. I was a big fan of hers. We got along great."
She also got along with Diamond, despite her character rejecting his countless advances. Last year, the pair found themselves working side-by-side again, this time on an indie film called Little Creeps.
But the girl Diamond knew from Saved by the Bell looked more like the woman he saw while recording a commentary nearly a decade ago. Diamond recalls her darting off set and creating tension when she was there.
"Part of me is putting it out of my mind and not thinking about it, but the other part is that of concern," he says. "Man, I hope she's all right."