Here's further proof NOBODY in the NFL is having more fun right now than Rob Gronkowski and Tom Brady ...
Coming off their Super Bowl win (and the endless stream of ensuing partying) ... Gronk decided to play around with TB12 with an epic FaceTime prank -- and it's hilarious!!
Check out video Rob posted Thursday ... the 31-year-old tight end called up Brady, just to immediately tell him that he's "busy right now" and needs to call him later.
"Did I call you!?" Brady asked with a perplexed look on his face.