In the Martial Arts episode, Penn, in a ridiculous tie-dye karate uniform, teaches his own pacifist martial arts to children that involves pouring chocolate shake all over your head.
The "Ouija Boards and Near Death Experiences" episode gets ever more ridiculous; from the ouija board that still works upside down to the people who believe their dog has been re-incarnated three times until, with perfect comic timing, Penn announces "then there's this fuckin' guy..."
Professor Best: "We didn't interview Professor Best just because of his last name but we did tell Professor Worst to go fuck himself."
The Area 51 episode has a hilarious spoof of the whole "alien conspiracy" with the Running Gag of "Box 51" in which Penn claims a box Teller is holding contains Hitler's brain due to Teller neither denying or confirming said brain is in the box.
Penn: (Box begins to twitch) Not only does Box 51 contain Hitler's brain, but it can dance! (smoke emits from the box and lights flash from inside as well) And it's on fire!
In the Video Games episode, one guy claims that FPS's "train" kids to shoot. They wordlessly tear apart the idea that mainstream video games can train you for anything by showing Teller calmly playing Wii Tennis, then having a real tennis player hand him a racket and serve him a ball. It doesn't even look like Teller sees the ball.