Black posted an Instagram video a few days ago in which he said, "I'm calling you out, Thor. This is a challenge!"

This is a challenge! #SchoolOfRagnarok @chrishemsworth @taikawaititi

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In his own Instagram video, Hemsworth admitted that he is "guilty as charged" when it comes to using the same song Black did in his 2003 comedy "School of Rock." And he's more than willing to battle... if he just could figure out what Black means by "jam."

in response to @jackblack #schoolofragnarock #jam @taikawaititi @marvel #thorragnarok

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Hey, we're ready for "School of Ragnarok." Bring it!