In all the old movies, smoking a cigarette sometimes signifies that the smokers have had sex, usually illicitly (like in "Now, Voyager"). I was exposed to a lot of these movies in childhood, and one day my neighbour and my aunt both started to smoke. I was about five, and I ran in screaming that Auntie was having sex with the neighbours (whatever *that* meant). I tell you, the looks on my mom's and cousin's faces were priceless.
A childhood belief about smoking

others believed things like this
- I used to think actors in movies sometimes had to actually die to make the movies look real.— Dero
- I used to think that clouds were caused by cigarette smoke— Monkey Dave
- I used to believe that "sue" meant murder, so in movies when someone is getting sued I got really confused— I don't know
- I used to think that my dad was "smoking pot" when he would smoke his pipe while sitting on the toilet. Anon
- I used to believe that priceless meant free.— Neo
- I used to think that "priceless" meant free.— DAAA