There are all kinds of crazy signs if you watch for them. Another favorite local sign of mine is the one at the exit to the local Costco parking lot, near the loading dock. It says, "Attention drivers--be sure the fork lift operator is out of your truck." You just know that at least one fork lift operator had an unplanned trip to Ohio at some point. As is the case with most of these signs, someone must have tried it.
We were in Atlanta a few years ago and visited the Georgia Aquarium. On the list of prohibited items posted at the front door was "fishing tackle." I asked a guard if people really tried to bring in fishing gear. He said, "Oh, sir, they try to bring in everything." I can see someone going home exclaiming, "Hey Betty Lou, I caught me a three-hundred pound grouper!"
Some of these I have had experience with or know someone who has. Most cardboard windshield sun shade have a legend, "Warning: Do Not Drive With Sun Shield in Place." I have to confess that I have moved cars a few feet with the sunshield in place. Not a good idea, I know. Some irons have labels, "Do not attempt to iron clothes while wearing them." We know a woman, otherwise sensible, who ironed her skirt while wearing it. Second degree burns. She knew as soon as the iron touched the fabric that this was a bad idea. My dad bought a cordless electric razor the included the warning: "Do not use under water." Like I said, somewhere, some time, someone has tried that.
I read about some others. On a Magic 8 Ball: Not advised for use as a home pregnancy test. (Too bad--it would save messing with urine.) A roll of Life Savers included these words: Not for use as a flotation device. (Do ya think?) On a disposable razor: Do not use this product during an earthquake. (Ow! Ow! Ow!) And on children's alphabet blocks: Letters may be used to construct words, phrases and sentences that may be deemed offensive.(The same is true of the alphabet in general.)
Our favorite sign, though, was posted in a store in Key West. It said, "Unattended children will be given an expresso and a puppy." I think that is warning enough.