Three bank robbers: a redhead, a brunette, and a blonde.
Are trying to evade the police when they come across a farm. Being short on time and options, they all decide to hide in the barn. The redhead hides near the horses, the brunette hides near the cows and the blonde hides in a pile of potatoes.
When the police come to search the barn, first they come to the horse stables.
The redhead lets out a hefty "neeeyyyy", the cops are convinced that the horses are indeed alone, and the redhead escapes.
The police then search the cow pens.
The brunette saw what the first robber had done, and belts out a deep "mooooo". The cops are again convinced and the brunette is able to escape.
The police finally turn to the stall where the Blond has hidden. The blond, seeing how easily the other two had gotten away, decides to use the same method.
So as the police officers came close they suddenly hear: "Potato!"