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Winnie Cooper, my how you've grown!

"The Wonder Years" star Danica McKellar got a sexy video vixen makeover for Avril Lavigne's upcoming "Rock N Roll" video.

Sporting blue fishnets and a "Mad Max"-inspired crop top and denim jacket, the 38-year-old math wiz (and mother of one) looked ready to rock, showing off her very impressive abs.

The former actress-turned-New York Times bestselling author finalized her divorce from ex-husband Mike Verta earlier this year ... and, looking like that, she's gonna have no problem moving on!

So far, we see no connection between Avril and Danica, so it's a pretty random pairing ... and we can't wait to see how the final video turns out!

"Thank you @danicamckellar for acting in my video. You are beautiful and so sweet. We kicked butt today! #ROCKNROLL," Avril tweeted after the shoot.

"Just had the best time shooting @AvrilLavigne's new video. And she is so sweet and fun! Made me feel like a rock star," added McKellar.

Lavigne also shared a photo of the two of them on set:

See how more former child stars have aged in the gallery above. Some of them may surprise you!

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