* CreatorBreakdown: Creator/BillMurray was going through a divorce during filming, which, coupled with arguments with Creator/HaroldRamis over what direction the movie should take, led to their friendship breaking down.
* DuelingMovies: ''[[http://www.imdb.com/title/tt0106188/ 12:01]]'', though it's an expansion of the [[http://www.imdb.com/title/tt0098962/?ref_=tt_trv_cnn 1990 short of the same name]], ''12:01 PM''.
* EnforcedMethodActing:
** See MistakenForGay on the main page, and then realize that that scene was ''improvised'' by Bill Murray; Ned's reaction was largely genuine. StephenTobolowsky (who plays Ned) is a great character actor, and did plenty of improvisation in the film, too.
** As is usual for Bill Murray, when Rita slaps him, she really does hit him hard. Not surprising, since all of the abuse Murray suffered from Carol Kane in ''Film/{{Scrooged}}'' were real as well.
* RealLifeRelative: The m,ayor is played by Bill Murry's brother, Creator/BrianDoyleMurray.
* ShrugOfGod: How long Phil spent in the loop. Harold Ramis said it was ''10,000'' years, while Bill Murray mentioned they discussed it and decided on "about ten years" (widely thought to be the "correct" answer).
* ThrowItIn:
** In the DVD commentary, Ramis claims that all he had planned for the scene in which Phil punches Ned Ryerson was just a simple faked punch. Toblowsky, who admits he can be a LargeHam sometimes, turned it into a full-on spin-and-stare-directly-into-the-camera-then-fall maneuver in reaction to the punch. And did so on every single take they tried. Eventually, Ramis just threw it in.
** After Phil smashes the radio, ''it keeps playing "I Got You, Babe"''. However, that wasn't ''supposed'' to happen. It was such a wonderful, dark moment that Ramis left it in.
* TypeCasting: Mostly Bill Murray, alternately played straight and inverted during the course of the movie, but a couple of the others could be described as such too.
-->'''Creator/RogerEbert''': The Murray persona has become familiar without becoming tiring: The world is too much with him, he is a little smarter than everyone else, he has a detached melancholy, he is deeply suspicious of joy, he sees sincerity as a weapon that can be used against him, and yet he conceals emotional needs.
* WhatCouldHaveBeen:
** The original script featured the explanation for the unending loop and its escape clause,[[note]]it involved a curse by an ex reading a "how to do magic" book[[/note]] but they found by [[DoingInTheWizard leaving it out]] made the film more magical.
** They flirted with the idea of a DarkerAndEdgier film, by taking full advantage of the no consequences mentality, (major cruelty, murder etc.), but they decided not to, realizing a more light-hearted comedy would appeal more to the general audience.
** The original script had a HowWeGotHere structure, opening with showing Phil going through a day from beginning to end and leaving his knowledge of everything a mystery before flashing back to the start of the time loop.