It's a pub quiz staple every film buff worth their ticket stubs will be able to answer: Arnold Schwarzenegger played which model of Terminator in the 1984 sci-fi classic?
To which you would immediately write "The T-800", because you're good at pub quizzes and possess a memory like a steel vice.
But do you know how many models of Terminator have been depicted in the film's growing franchise? Could you tell the difference between a T-600 and a T-850?
No, us neither. Until we studied this superb video guide from iO9, cataloguing every metallic killing machine from the Terminator films and video games (which you shouldn't bother playing).
Consider it revision for the next film round.
(Images: Allstar PL)