Someone in the comments said they almost feel sorry for the guy. But I believe this was planned - here's why. The camera (phone) was already recording as mister prat-fall was about to enter the picture. Notice where it was pointed. At the counter. Why? Nothing happening there, no reason to be recording. Unless, you know your buddy is about to make a spectacle of himself while dressed in drag. Then you're ready for him to enter the picture.

There was very little camera movement since the guy knew exactly where his buddy would be taking his dive. Then, when the guy takes his fall, he does so in an exaggerated way, wig flying off, legs flailing and splaying, etc. And notice how he didn't scream or yelp, which would be the natural thing for someone to do if they fell unexpectedly. The guy didn't yelp because he knew he was going to fall - on purpose. Notice that when he 'tries' to get back up, he slips and slides all over the place, with great agility. Again, on purpose. Why was he using a walker when he entered the frame if he can move his legs so well? Such great athleticism proves he didn't need it. Pure prank - 100%.