updated 10/04/2012 AT 7:00 AM ET
•originally published 10/04/2012 AT 4:50 PM ET
“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.