Actress Shirley Henderson — who played Moaning Myrtle — was the oldest actor or actress to play a student in the films, first appearing aged 37.
Harry’s eyes in the films weren’t the vivid green described in the books because Daniel Radcliffe’s eyes reacted badly to the contact lenses.
Ian McKellen was offered the role of Dumbledore, but turned it down.
Three different owls were used to play Hedwig in the films — Gizmo, Ook and Sprout.
Sirius Black’s tattoos are borrowed from Russian prison gangs —they identify him as man to be feared and respected.