My Boss's Free Haircut - S4-E20
Other mistake: When Bob is trying to get into the patients room, he uses a screwdriver to break in. The door opens into the room with the hinges on the inside, theres no way he could get at them and the door frame is intact as shown when the door falls in.
Other mistake: When Turk is squirting cream on to the pancake to make a face, we hear 3 squirts which wouldn't be enough. The eyes are X-shaped and would take 2 each plus the smile would have taken a longer squirt.
My Ocardial Infarction - S4-E13
Other mistake: When J.D. is left dangling from a window after the collapse of the "triple giant doctor," his feet are higher up than the combined height of Lonie and Elliot.
Other mistake: When the Janitor plays with Kelso 'double or nothing' for tossing the cotton ball a second time in the jar, Todd tells Kelso he now owes him $600, in the end it was $700. This isn't a 'double or nothing' amount of money the Janitor could generate. They started with $5, so the count would be 5 - 10 - 20 - 40 - 80 - 160 - 320 - 640 - 1280 and so on.
Answer: No, it was a fake, they used a stamp.
It is real.