It's staged. At the end of the Prank video that Frank did, they had a slo-mo of Jon slapping Pink Guys ass. They just set it up so it looked like there was just a random cameo stopped on the street. It's a bit like how H3H3 gave a dollar to Frank in his Helping the homeless video, assuming he was homeless and that they didn't know each other. Oh but they do. The memelords have united.