Factual error: A very common error in First World War films. British soldiers were not permitted to shave their upper lips until 1916 - in 1914 almost all (unless physically unable to grow them) would have had moustaches.
Factual error: One of Angel's lyrics (in "Today For You, Tomorrow For Me) refers to the movie "Thelma and Louise." Rent (the movie) is set in 1989-90. "Thelma and Louise" was released in 1991. This was caused when they did the move from Broadway to the screen. The stage show did not specify the year. So when they adapted the stage show to the movie, they didn't check the references. Plus it just sounds cool. (00:28:25)
Revealing mistake: Towards the end when Harmony calls Perry's phone as she's lying on the ground, Harry grabs the phone and looks at the caller ID to see her name. Unfortunately that's not the display showing who's calling. Anyone who has a Nokia phone will recognise that that's showing the contact list with just two entries - Harmony and a random number. The fact that it says "contacts" at the top of the screen is a bit of a giveaway.
Continuity mistake: When Samantha is sitting at the foot of the bed with an ice pack on her head, eating toothpaste, in one shot she spits some toothpaste out and it goes over Chris' hand. In the next shot his hand is clean. (00:36:55)
Continuity mistake: When Minty arrives at the North Pole in a balloon, she passes Santa's house twice.