P and Q - From when old printers had to deal with letters that looked

From when old printers had to deal with letters that looked like they were drunk and upside down.

My teacher says, 'Watch your P and Q or I'll make you write the alphabet 100 times.'

The printer guy yelled, 'Watch your P and Q or I'll smash your type!'

My dad says, 'You're as messy as a printer with bad P and Q.'