According to director Christopher Landon, Tree's punchline, "Who takes their first date to Subway? It's not like you have a foot-long," was improvised by Jessica Rothe.
The Bayfield University Baby killer costume was designed by Tony Gardner, who also designed the Ghostface mask, the horror icon of the Scream franchise and which is a reworked version of the Father's Death Halloween costume.
Director Christopher Landon tested wearing the option of a baby mask for the killer in the office and scared a worker, confirming his choice.
The scene where Tree walks through the campus quad naked had to be done quickly; given that it was being filmed on an active college campus, this presented the risk of students witnessing the scene being filmed and/or taking photos. The crew took extreme precautions to clear away any potential onlookers. In the end, they managed to do just 2-3 takes.
The theatrical trailer utilizes the song "In Da Club" by 50 Cent as Tree's birthday ringtone. However, the final film does not feature this as the crew and studio could not acquire the rights. As a result, an original ringtone composition was concocted.
When asked why a baby mask: Christopher Landon says he needed a combination of something that would pass for a mascot on a college campus, that was both scary and funny at the same time, plus he was expecting a son at that time, so he had "baby on the brain."
The original script written by Scott Lobdell included material intending to make the film R-rated. Some scenes involved grislier death depictions that were entirely altered by the film's director Christopher Landon.
The original mascot and mask designed by Tony Gardner for the killer was a pig, a motif already done in the Saw movies.
Jessica Rothe described her nude scene as "liberating" because an all-female film crew shot the scene.
The scenes where Tree leaves Carter's dorm room and walks through the campus quad, with the same specific events happening each time (i.e. The couple getting soaked by the sprinklers, the car alarm going off, etc.) took two days to shoot. At one point, the sprinklers malfunctioned and couldn't be turned off, costing the crew at least an hour of filming until they were finally able to fix it.
Even though they only filmed and show her face and bare back in the movie, Jessica Rothe said in a 2017 interview that she decided to go totally nude for the scene where Tree walks around campus naked in order to feel the same rush as her character. She called it a very "liberating" moment. "It was incredibly freeing. I think everyone fantasizes about what that would be like if you kind of just got to live life without repercussions and do whatever you want, and what that bucket list would be. Not only did I get to play someone doing it, but I got to do a few of those moments, like the naked walk of glory--not walk of shame, walk of glory. It was one of the most empowering experiences I've ever had in my life. And a huge part of that was I trusted [the director] so much, and to portray that in a way that I felt comfortable. The crew was incredible." She explained that when they shot that scene, all the women of the crew would surround her holding up their jackets, shielding her from outside eyes and cell phones so footage of her stark naked couldn't be leaked onto the internet. The women would chant her name and she would do a little dance in the middle between takes to get pumped up. "Then as they yelled, 'Action,'" she added, "they would disperse, and I'd do my little walk, and they would all come and cover me up at the end. I just felt such love and female awesomeness in that moment. It's something where I could have a very long and successful career, and never get to do that again. So there were a lot of amazing moments filming this."
The script was written back in 2007. It was going to star Megan Fox and was to be produced by Michael Bay, which may explain the name of the school in the film, Bayfield University.
Tree's shirt says "Dumpstaphunk" on it. 'Dumpstaphunk' is an actual funk and jam band from New Orleans, Louisiana.
Rachel Matthews (Danielle) is granddaughter of the late Michael Landon, famous for Little House on the Praire, and therefore she is niece to Christopher Landon (Director).
Tree's birthday is September 18th. You can see the date when she looks at the alarm clock and realizes she's late for class.
The creator of the freaky King Cake Baby character, which is used as one of the New Orleans Pelicans mascot has sued the creators of Happy Death Day for stealing his mask.