I used to think that as 'a few' rhymed with two, therefore it meant two. My brain didn't register that a couple of people weren't three of them.
A childhood belief about counting

others believed things like this
- I used to believe that, in a deep and profound kind of way, the words "door knob" rhymed with "said so". — Katie
- I used to think the lady behind the cash register at the A & P got to keep all the money in the drawer.Anon
- I used to think that "No standing signs" meant that you weren't allowed to actually stand in the area!Anon
- I used to believe that people who wear glasses did had a second brain!— Onessa
- that the word "couple" as in "a couple of items" was synonymous with "several", rather than "just two".— Blair A. Petterson
- I used to wonder why they didn't fix the Leaning Tower Of Pisa. Weren't they embarrassed that it was crooked?— Bootlebat