Variations:
Sometimes the intended victim is found abandoned in a bathroom, partially disguised (e.g., hair cut, clothing changed), or implements for altering the child's appearance (e.g., scissors, razor, hair dye, wig, clothing) are found in a bathroom stall.
Sometimes the kidnapper is caught attempting to escape through an exit with the disguised victim (often because the parent recognizes some detail of the child's clothing the kidnapper has neglected to alter, such as shoes).
The child is often found to have been drugged (to make it easier for the kidnapper to alter the child's appearance and smuggle him out an exit).
Although this warning is undeniably good advice, the legend that presents it exaggerates both the prevalence and manner of kidnappings. A child is far more likely to be snatched by a family member or ex-spouse in a custodial dispute than he is to be the victim of a random abduction. And rarely will kidnappers go through such elaborate procedures as the ones hinted at here -- luring a child outside where he can be quickly bundled into an automobile is far more effective and less risky than trying to smuggle one out the exit of a crowded public space. (The example presented above doesn't even make much practical sense. Why waste precious getaway time shaving a child's head -- with a razor, yet -- when you already have a wig to cover its natural hair?)
This type of tale that has been circulating for decades, always involving the kidnapping of children from family-type public places such as amusement parks and shopping centers. A kidnapper snatches a child away from an inattentive parent, drugs it, and hustles it into a restroom; there the abductor performs a quick haircut, dye job, and clothing change on the child to conceal its identity (and sometimes to obscure its gender) and wraps it in blankets before attemping to quickly and quietly spirit the child off the premises. Meanwhile, a vigilant security force has sealed off all the exits, and the attempted kidnapping is thwarted either because the kidnapper realizes he cannot escape undetected and simply abandons his intended victim in the bathroom, or because the child's parent is monitoring the exits (in person or via security cameras) and recognizes the child by its distinctive shoes, which the kidnapper has neglected to change or remove.
More malevolent versions of this story end not with the thwarting of the abduction attempt, but with the discovery of the child's original clothing on a restroom floor (along with other evidence of what had transpired, such as loose hair, scissors, and a bottle of hair dye). In these versions police tell the victims' parents they are powerless to recover their children (whom they warn are probably already on their way out of the country to be used as unwilling organ donors or sex slaves), and the parents are paid off to keep quiet about the abductions. Often the payoff for the parents' silence is claimed to be something absurdly small in value, such as free passes to the amusement park where the kidnapping took place, yet people continue to take the story at face value. Would you keep quiet about your child's disappearance for any amount of money, much less something as paltry as a few free tickets?
Since the details of urban legends tend to localize on the most prominent examples of their kind, this legend has become more and more associated with places such as Disney theme parks and Wal-Mart stores, both examples of well-known large facilities frequented by families with children, and both part of huge corporate enterprises. (In truth, no child has ever been kidnapped from a Disney theme park, and although the abduction and murder of 6-year-old Adam Walsh led Wal-Mart to create their Code Adam protocol for locating missing children in their stores, Adam Walsh actually disappeared from a Sears outlet, and no evidence was found to indicate that the abductor had made an effort to alter Adam's appearance.)