- Banned in China: Not the movie itself, but the shot of Tree's nude backside when she goes Streaking.
- "Common Knowledge": It was widely thought that Tombs' first name was Joseph, with many articles, and even several wikis formerly referring to him as 'Joseph Tombs' despite being called 'John Tombs' in both the film and the end credits.
- Dawson Casting: The two leads were way past college age, with Jessica Rothe already 30, and Ruby Modine being 27.
- I Knew It!: Some viewers of the trailers guessed that Lori is the killer, because the candle she drops to ignite the gasoline is similar to the one from the cupcake she gave Tree earlier, which is shown in the trailers.
- No Budget: Much like most Blumhouse Productions movies, the movie was made on a very low budget (in this case, $4.8 million).
- Real-Life Relative: Rachel Matthews, who plays Danielle, is the niece of director Christopher Landon.
- Serendipity Writes the Plot: The scene after the killer dies was supposed to be in the sorority house. However, once it was time to shoot the filming permit in the campus was over, so Tree and Carter watch the fallout in a diner (which not only was in Los Angeles, far from the Louisiana location, but had also appeared in another Blumhouse production, Split).
- Throw It In!: Jessica Rothe improvised a few of her lines, most notably "Who takes their first date to Subway? It's not like you have a foot-long."
- What Could Have Been:
- Megan Fox was considered to play Tree.
- The killer originally wore a pig mask, most likely changed to deviate from Blumhouse's The Purge sequels that also depict serial killers dressed like pigs.
- Originally, there were two killers, with Gregory Butler working alongside Lori to murder Tree. Landon wasn't fond of this idea and had it removed from the final draft.
- In the scene where Tree is drowned, she would take off the mask to learn who the killer is - but given her head was underwater, she couldn't discern the face. Budget and time constraints forced the idea to be scrapped.
- Michael Bay was originally set to produce the film.
- In the original ending, Stephanie Butler turned evil and killed Tree at a hospital, doing so in an act of revenge. Being such a downer, test audiences hated it.
- Working Title: Half To Death.
Trivia / Happy Death Day