I used to think that a mug shot was a picture of the criminal that was put onto police mugs which were then handed to cops all over the country so that they could recognise the bad guy.
A childhood belief about criminals

others believed things like this
- I used to think that tea grew on trees already in mugs!Anon
- I thought the song "Karma Police" was actually saying "call the police" before I learned the title— Alberto Richardson
- When I used to see the sign 'police accident' I thought it meant that a police car had crashed.Anon
- Until I was about 11 or 12 I thought that "prostitute" referred to a female criminal.Anon
- I used to believe that guns shot out blood because everytime somebody shot a gun in a movie you saw blood.Anon
- I used to believe that undercover cops hid under covers/sheets. — Holly