In the episode featuring Dimples, Jon and his experts watched as a cook was cooking a medium burger and ended up burning it. Near the end, they were yelling, "Flip the burger!".
In the episode "Piratz Tavern", the head "chef" Jucianno attempts to show his "signature dish" to the chef Taffer brings in, having never tasted it himself. They are basically strips of chicken with enough red-hot pepper spices on it to qualify as chemical weapons. The chef is nearly overwhelmed just by getting a scent of it, and when he tries a bite he has to instantly spit it out. Then the chef tells Jucianno to try it, at which point he almost immediately wheels around and spits it out into a trash bin.
In the episode featuring Chileen's, a horse walked into a bar. Yes, a live horse was rode into the bar in front of Jon.
During "Zanzibar's", one of the first things that happens to the poor undercover patrons is that a guy who has been way over-served sits next to them and tries to talk to them. What comes out is complete gibberish. What does it mean? God only knows.
Drunk Guy leans back like he just imparted great worldly wisdom. Mystery Diner turns away with a "what the hell was that" look aimed right the camera.
James' antics throughout the Cashmere episode, which included walking in the women's restroom, ripping off his shirt while DJing, sitting on the bar top itself and pretty much acting like a tool to everyone he interacts with. All while saying "All in!".
The Whip noise effect that plays every time he says it just makes it funnier.