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Now that the Gronk Party Cruise is over, Rob Gronkowski has to find another means of having fun this offseason, so he did what exactly what you'd expect him to do: He called up Richard Sherman and invited him to go tandem biking. 

Actually, that's not why the two were tandem biking together. Gronk and Sherman recently spent the day together to film a commercial for Oberto beef jerky and ESPN.com caught some behind-the-scenes footage of Gronk and Sherman's day of fun. 

Not only did they ride a tandem bike, but the duo also took some time to try and figure out how to solve a Rubik's cube. Gronk has the right idea here, he's painting his cube (screengrabs via ESPN).

Gronk also took some time to prove that's he the Leonardo Da Vinci of etch-a-sketch.

Finally, you can't hang out with someone and not wear Snuggies together, so that's exactly what Sherman and Gronk did.

You can see an outtake below of the tandem bike riding experience that Gronk and Sherman had together. The only way the clip could be any better is if Gronk hadn't ended it with, "You know, you guys really should've given the ball to Marshawn."