One of Hollywood's sexiest geeks, indeed.
The 37-year-old teen star turned math whiz sported the teeniest of tiny skirts over fishnet stockings that left zero to the imagination.
Let's just say, the title of McKellar's 2012 opus, Girls Get Curves: Geometry Takes Shape, has taken on a whole new meaning. (Or at least the existing double entendre just got raised to the 10th power.)
Her look is rounded out by a plunging crop top (nice abs, Miss Cooper), an even more cropped denim vest, stilleto-heeled booties and some wacky headgear.
It's like Wonder Woman meets She-Ra meets The Runaways. Surely just as Avril intended.
"Rock N Roll" is the second single off of the newlywed's upcoming fifth studio album. Both Lavigne and hubby Chad Kroeger are among the songwriters listed on the Max Martin-produced track.
But while Lavigne declares in the tune that she's the "motherfreakin' princess"...she better make room for another booty on that throne.
McKellar lends her voice to the animated series Young Justice and she appeared earlier this year on an episode of The Secret Life of the American Teenager.
What do you think of Danica's punk-rock look?