Self-described "fat actress" Kirstie Alley is so terrified of taking to the ballroom floor Monday evening for the premiere of 'Dancing With the Stars' that some insiders are worried she might be too scared to actually dance.

"You have no idea how nerve-wracking that first dance can be in front of a live audience in the ballroom, the judges and millions of viewers that are watching from home," an insider tells me. "Rehearsals help you make all the right moves, but dancing on an empty stage and blocking out your routine with the cameras is very different from going live."