It's been 20 years since Sixteen Candles, and we still can't believe Sam (Molly Ringwald) gave her undies to a geek. Nor can SNL's Tina Fey, who rewatched the teen classic while penning her high school comedy, Mean Girls -- and learned how times have changed. There's no nudity or swearing in Girls, but a masturbation joke almost landed it an R rating. (The MPAA agreed to PG-13 after the line was tamed.) In the PG-rated Candles, one of Ringwald's ''first lines is 'They f -- -ing forgot my birthday,''' says Fey. ''The panties, Long Duk Dong -- it made me think things have tightened up.'' Still, Girls' kid-friendly rating helped it to a $24 mil opening. ''Imagine an R-rated Lindsay Lohan movie? There would have been rioting in the streets!''