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The old tumbler that supposedly caused the side effects.

The McDonald's Happy Meal was introduced in 1979. One of the original toys available with the meal was a small plastic tumbler with Ronald McDonald on the side. Children who drank from these tumblers allegedly suffered varying effects including hallucinations, emotional and physical outbursts, blisters around the mouth, and increased physical strength. A 5-year-old girl from St. Louis, Missouri reportedly was able to "toss a car with such force that several pedestrians [were] critically injured". No person over the age of fourteen was affected by drinking from these tumblers.

Most of these tumblers were either destroyed by the McDonald's franchises or otherwise lost. Every few years, one of the tumblers will show up on eBay, but the auction is usually deleted from the system within minutes of being posted.