I'll leave you to try to guess what they are really represent (or you can click through to the link to find out), but here's my initial thoughts:
Warning Ninja Nuns on Board - April 1979
Beware of Charlie Chaplin impersonators - July 1976
Transformers will turn you into monsters if you behave incorrectly.
The last one is actually from 1982 but was my personal favourite.
Compare these to "Please do this at home" campaign from 2008 and you'll see the Japanese have now gone for a more obvious approach. It must be a difficult balance from being clear & literal & maybe a touch patronising, to being so creative & running the risk of few understanding what you're trying to say.
Do you think these would work on the London Underground? Have you seen any posters which you think are too cryptic?