For one of Tyler Posey's shirtless nighttime scenes in the woods, creator and writer Jeff Davis wanted to show solidarity with his young star in the freezing temperatures and removed his shirt too. Davis lasted all of 14 seconds.
Tyler Posey has a large tattoo on his body that has to be covered up for all of his many shirtless scenes.
Director Russell Mulcahy cameos as the owner of the pool into which Scott falls when he runs from a werewolf in the woods.
The teacher in one of the school opening scenes misspelt 'Kafka' and 'Metamorphosis' so the correct spellings had to be CGI-ed in.
Dylan O'Brien (Stiles) kept the "Beatles" shirt Stiles is first seen in and wore it to the nine year reunion.