During the police chase when Phil is being chased down the railroad tracks, the police car has a rotating light bar. In close up shots the police lights flashing behind the vehicle are clearly strobe lights.
On the first day Phil wakes in the hotel, he looks out of the window and sees certain cars moving and turning. The next day (at around 19 mins) he looks out of the window again and sees exactly the same cars etc. as though it is exactly the same time, but the time is different based on the radio show that is at a different point.
When Phil takes his "joyride" with Gus and Ralph, there isn't any snow, but the blizzard would already have hit the town by then.
On February 3rd, when Phil and Rita are leaving the place Phil has been staying, the shots of the gate in the fence show the gate closed in the shots from near the building, but show the gate open in the shots from the street.
When the police are chasing Phil in the Cadillac convertible, he wrecks into a row of cars, the first one being a 1983 AMC Eagle wagon. In the next scene, the Cadillac is crashed against a small Chevy, and the Eagle is on the other side of the Chevy.
Sunrise in early February in Punxsutawney, Pennsylvania, is not until around 7:25 am, so at 6 am it would still be fully dark.
(at around 49 mins) In the Bavarian restaurant, a poster appears on the wall reads "Alles Gute Zum Erdhörnchentag". This is supposed to mean "Happy Groundhog Day", but is, however, a mistranslation because "Erdhörnchen" means "Gopher". The poster should have read "Alles Gute Zum Murmeltiertag".
In the first scene where the bed & breakfast is shown, it is 5:59 a.m., and it's already light outside. In Punxsutawney, PA the nautical twilight is at 5:51 a.m. on 2 February and in Woodstock, IL where the movie is filmed, the nautical twilight is not until 6:02 a.m. It is not possible that it would be as bright outside as depicted in the film.
In the groundhog weather predicting scene, one of the officials holds up a sign that reads "Punxsutawney Penn. Weather Capitol of the World." The correct spelling in that context would be "capital."
Phil apparently removes the distributor cap and leads from the engine in a Dodge van. The engines used in this vehicle have the distributor located at the rear of the engine. It is only accessible by removing the interior engine cover, not from under the hood.
Phil is never seen trying to leave first thing in the morning before the highway gets blocked, but that doesn't mean he didn't try, fail, and give up. There could be many things he tried that aren't shown before he finally decided to settle down.
Phil, Rita, and Larry arrive in Punxsutawney, and, as they get out of the van, Phil announces he's not willing to stay in the hotel and Rita tells* him he's got a reservation at a Bed & Breakfast across town. Phil is thrilled and climbs back to the van, in the passenger's seat, but there is no driver, because the driver is Larry and he is staying at the hotel. *Rita says: "Larry's just dropping me off. I got you a reservation at a nice bed and Breakfast."
Phil says, "Well maybe the *real* God uses tricks, you know? Maybe he's not omnipotent. He's just been around so long he knows everything." Although knowing everything is omniscience, not omnipotence, Phil is not confusing the terms. The point of his statement is whether omniscience can give the appearance of omnipotence, as Phil himself demonstrates through his various deeds (both selfish and selfless) throughout the movie, which to someone outside his point of view may appear to be akin to omnipotence.
When Phil is driving his car down the quarry ravine in a suicidal attempt, there is clearly no driver visible.
While on his death binge, the pickup truck Phil uses to drive over the cliff clearly has no engine or drive-train components. The underneath shot is even depicted in slow-motion, and one can see clear through to the radiator.
When Phil is being chased in the truck with the groundhog, they pass under a low bridge which is too low for the TV truck to pass under, however the TV truck is still in the chase in the next scene.
Phil's room in the Cherry Street bed and breakfast is on the top floor overlooking the street. The sizes and number of windows inside his room do not match any combination of those from the exterior shots, which is due to the fact that the interior shots were not filmed on location.
When Phil is helping the ladies with the flat tire, he's using a jack to raise the car. Two shots are used (one showing Phil, the other showing the ladies in the car) as Phil is jacking the car up. But the car never gets any higher off of the ground like it's supposed to. It just bounces up and down to the original starting point.
As Phil walks off the stage after performing the piano number, two background actors behind him are visibly 'fake clapping', but there is no clapping sound to accompany it. Whilst this is a technique used on set when recording dialogue, so the background actors' clapping does not get recorded by the actors' microphone, for some reason the sound editor missed this or decided not to dub it with 2 people clapping, giving this strange looking result.
In the last part of the movie, Phil is seen playing the piano on stage at the party. As he finishes up song before going and talking to Rita, the piano in the soundtrack is playing a glissando (running a finger rapidly down the keyboard) while Phil is still playing as he was before. Finally, at the last run, Phil's hands match the sound.
As Larry films the flaming wreckage of Phil's truck in the quarry, the lights used to create the glow of the fire can be seen reflected in the lens of Larry's camera.
The snowman's head rotates with geometric precision, revealing it's a prop mounted on a vertical rod.
Phil wakes up at 6am every day to bright sunshine outside, however sunrise in Punxsutawney doesn't happen until 7.26am so it should still have been dark.
Although the movie is ostensibly set in Punxsutawney, when Phil meets Ned for the first and subsequent times there is a store in the background quite clearly named 'Woodstock Jewellers', obviously named for the town where the movie was actually filmed.
On the third morning, Phil rushes out of the hotel without interacting with the chubby guest and the female hotel proprietor, which should put him ahead of schedule. However, as he exits the hotel, the piano teacher has already crossed the street, and his encounters in town (e.g., Ned) occur on schedule.
Phil's morning routine varies from Groundhog Day to Groundhog Day, e.g. the amount of time he spends in the breakfast room or talking to other guests or the proprietor, but he meets Ned at exactly the same point of time and location every time.
At the party scene at the end of the movie, Phil's piano teacher screams "That's my student!", when Phil plays the piano. This shouldn't be the case as the teacher was paid with a bag of cash Phil stole from the back of the money truck, and the day that let Phil out of the time loop was the day where he only committed virtuous acts. As such, Phil shouldn't have been able to bribe her into being his piano teacher in this iteration of the loop.
When Phil plays piano with the jazz band, his piano teacher is glowing. She says that she is his piano teacher and that she is so proud of him. Unless he had a piano lesson that same day, she'd have no memory of teaching him. If he did take a lesson that day, she would have encountered an accomplished piano player and she would not have been taking any credit for teaching him.
In the diner, when he's proving that he knows about everyone, Phil introduces Rita to "Debby Keisler and her fiancee Fred." At the Groundhog Dance near the end of the film, Phil introduces the pair, now married, as "Debby and Fred Keisler." Either they already had the same last name, Fred took Debby's last name, or somebody screwed up.
When Phil is reading poetry to Rita back at his room, Rita dozes off. When she awakens, Phil says, "I think the last thing you heard was, 'Only God can make a tree'." This is a partial quote of the last line of Joyce Kilmer's famous poem "Trees". Unfortunately, either Rita must have been dreaming it, or Phil must have been quoting it from memory, as Kilmer's poem is not included in the book Phil is reading from, namely: "Poems for Every Mood", compiled and edited by Harriet Monroe in 1933.
When Phil and Rita first talk in the Bavarian restaurant, a waitress crosses carrying 4 large steins of beer. She sets them on the table behind Phil and Rita. Watch as she walks away from the table. She touches the shoulder of the older gentleman seated at that table and leaves foam on the top of his jacket sleeve.
Right after it's announced the very first time that there will be 6 more weeks of winter, one of the Groundhog Day officials in a tuxedo & top hat on the right hand side of the stage is shown holding a giant "BLIZZARD" sign upside down until someone in the crowd points it out and he turns it right-side up.