LOL - What I love are the obvious things that never existed when I was a kid like:
When you but nuts the packet says - Contains nuts!
Or buying a coffee from McDonald's - This coffee is HOT (I damn well hope so)
Or the wonderful sign at the hotel in Ibiza I stayed at last year - at the poolside it said -
If you cannot swim please don't swim in the pool!
Or the microwave I saw in Florida with the sign on it that said 'Please do not use the microwave for drying your pet" - I mean the idea would never have occurred to me but I assume some Floridian or perhaps more than one have done this...
These signs are not as wacky as you think. There are some cultures that use types of toilets you may not be so familiar with, such as squatting toilets (like a shower cubicle floor, with a huge hole and two raised spots for your feet). People from those cultures, when confronted with a seated toilet, are liable to try squating on it. To them, the idea of sitting on the same seat, with bare buttocks, as someone else has is grossly unhygenic.
I just had a dream about a Wes Anderson film called Rhythm about a family of cats that move into a house they have to renovate and they are a bunch of weirdos. Someone made it big in the lottery and the extended family move in and the scene was painting where they were experimenting with an undercoat of doodles of differing kinds of animals with captions. The things that minds come up with but it was definitely stupid.