Boil Bottles, Not Bunnies

So the other day, it went like this:

Me (puttering around the kitchen, singing to Wallaby--to the tune of Row Your Boat): Boil, boil, boil your bottles; gently in the steam! Merrily, merrily, merrily, merrily; life is but a dream … (back to talking voice) Remember, Wallaby, boil bottles, not bunnies, okay? Boiling bunnies is not recommended.

Arizona (coming into the kitchen to flip the bacon): Why?

Me: Why boil the bottles?

Arizona: No, why warn him against boiling bunnies in particular? Why not bleach or aerosol cans or something?

Me: You know. Boiling bunnies … from Fatal Attraction. (Getting a blank look.) With Michael Douglas? Did you see it?

Arizona: Yeah, but I don't remember the bunny boiling scene.

Me: Which goes to show that your exes have been generally sane. 

Back in the day, I remember reading a science fiction short story about a society in which certain things were given; they were called an 'everyone-knows thing' and treated as fact in the absence of evidence. Then along comes our main character, who manipulates a situation by saying that something is an everyone-knows thing when it isn't. The others around him, who can't conceive of a falsehood, assume they have forgotten this everyone-knows thing and accept it into their world view. And thus lying is born. 

(Google didn't provide much help in a search of 'everyone knows thing science fiction', although I found a few places where folks have used the term, so am pretty sure I'm not making up the story. It might have been in the Asimov or Analog magazines, or a short-story collection? Mad points to anyone who comes up with the title and author.)

Anyway, in my association with Arizona, I have come to find that certain things that I always took as everyone-knows things are more like 'things everyone in New England knows' or 'things me and my friends know' rather than absolutes. Like bowling with the little balls with no finger holes (candlepin, which is all I've ever known as 'bowling' and which Arizona finds entirely weird) or ordering jimmies on my ice cream.

What are some of your everyone-knows things that turned out to be 'things I know that I assume everyone else does'? For me, I'll add bunny boiling to the list, while Wallaby (in rock star mode with his hair and shades) laughs at us both.