Zack Morris Is Doing CrossFit Naked!

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Mark-Paul Gosselaar appears to still be up to his old Saved By the Bell antics -- only this time he's in the best shape of his life.

The 41-year-old actor posted a pic of himself hanging upside down with his animator pal Ben Ceccarelli, and both buff men are wearing nothing but a censor strip. "Teaming up with @Piketoon for the @CACrossFit #pairpower competition. @CrossFit. Some would say we've already won," he tweeted.

They appropriately titled themselves, "Team Cocky."

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Gosselear -- who portrayed Zack Morris on the beloved teen sitcom Saved By the Bell-- just can't get enough of CrossFit. On Wednesday, CrossFit Horsepower Dan Wells Instagrammed an image from a workout that included a shirtless Gosselaar.

Gosselaar tweeted a link to the pic, writing: "Spot the monkey."

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Looks like A.C. Slater isn't the only muscular guy to come out of Bayside.