The episode's called "Green Dress for the Red Carpet," but don't let the colors fool you; this isn't a holiday challenge. The green dress is what the designers must fashion -- using only eco-friendly fabrics and materials -- to impress the judges and mentor Joanna Coles.
In our exclusive preview clip, Coles shares her opinions on the designers' early plans, including Casanova's idea of attaching circular strips to the bodice of his dress.
"That looks a little weird when you do that," says Coles. "It looks a bit nipple focused."
Casanova is one of just eight designers left in the competition, so for his sake, here's hoping guest judge Diane von Furstenberg is considerably more impressed with his nipple focus.
"Project Runway All Stars" airs Thursday, 12/6 at 9 PM on Lifetime.