Happy Death Day (2017)

Continuity mistake: On the third and fourth day, Carter's roommate shows up earlier than the first 2 days. And Tree's suspect tips notebook every day don't reset and the line and erases are the same.

Continuity mistake: When Tree looks at her iPhone it shows the time as 9:23 when the power goes out. Then when the TV is shown the time on that clock is 9:24, when she walks to the TV the time is then 9:31, and then the next view of the clock shows the time back at 9:24.

Factual error: One of the deaths involves a burning candle, a car and a leaking fuel tank, resulting in an explosion. This wouldn't happen. Multiple independent test evidence that petrol/gasoline can't be ignited this way, a flame isn't hot enough. Only the fumes can be ignited, which isn't what happens here, and the tank wouldn't explode anyway.

Trivia: The plot of the movie is similar to Groundhog Day which is something that Carter mentions to Tree at the end of the movie. Tree's roommate's name is Laurie Spengler, which is a reference to Egon Spengler, played by Harold Ramis in Ghostbusters. Harold Ramis co-wrote and directed Groundhog Day.

Trivia: There actually is an in-universe explanation for why Tree got stuck in a time-loop. However, director Christopher Landon opted to omit it from the finished film. Partially because it could be used in a potential sequel, and partially because it wasn't necessary for the narrative. Landon has hinted that the upcoming sequel, "Happy Death Day 2U," will finally reveal the explanation.

TedStixon

Trivia: The killer's mask was designed by Tony Gardner. If that name sounds familiar, you're probably a big horror fan. Aside from the killer's mask in "Happy Death Day," Gardner also helped design the final look of "Ghostface" seen in the"Scream" franchise (albeit loosely based on an earlier design), worked on a number of cult-films including "Darkman, "Hocus Pocus" and the "Evil Dead" sequels, and has worked as the main effects supervisor on a number of the "Chucky/Child's Play" films.

TedStixon

Lori Spengler: How did you figure it out?
Tree Gelbman: Because you've killed me before.
Lori Spengler: Then I guess I'm just going to have to do it again.

Tree Gelbman: I can't change what I've done, but I can start trying to be a better person today.

Tree Gelbman: It's been so much worse.
Tree Gelbman: All of this running and hiding has made me so miserable.
Tree Gelbman: And I think I finally figured it out.
Tree Gelbman: For me, it took something, like, totally crazy, but.
Tree Gelbman: But I'm here.
Tree Gelbman: And I love you.
Tree Gelbman: And I'm so, so sorry that I hurt you.