Revealing mistake: When Anna and Hans are dancing in front of the lighthouse, we don't see the shadow of the railing or the ground they're standing on.
Revealing mistake: When Han shoots at Bruce Willis and the others with the Gatling gun, we see cartridges on the ground. You can tell that they are all blanks. The tip is jagged and has been closed - live ammo just has an open hole where the bullet was.
Factual error: The movie is set around 1995. But the SWAT team in the movie is wearing gear from the 2000s. (MICH-2000 helmet, modular tactical vest, M4 variant with picatinny rails and scope). Plus, in a scene when the guys are shopping for a taser (gun shop scene), some of the rifles on display are from 2000s era. AR-15 variants with variant stock, foregrip and picatinny rail. Those style of weapon system were unheard of in early 90s. Even Special Forces just adopted it by the late 90s.
Continuity mistake: In the scene where grandpa is attempting to ship his grandson to his dad in a cardboard box, grandpa says to the two ladies who are objecting to his requests "well give me a pen, and we'll write FRAGILE on it." Shortly before he says that, the box already says "FRAGILE" on the right hand side, and then 2 seconds later the writing has disappeared. (00:31:10 - 00:32:15)
Continuity mistake: When Teresa is yelling and hitting Jordan because he cheated on her with the blonde girl in the limo, the car disappears and reappears between shots. (01:00:35)
Continuity mistake: When Tom the Minion dressed as a maid is hoovering, he answers the front door by opening it towards him as does the minion who looks out of the door after Tom has been taken. In the scene with Gru sat on the steps in the rain, sad that Lucy is off to Australia, Agnes comes out with an umbrella, but now the door opens outwards.
Plot hole: They aren't able to travel before the birth of their children or their children become different. Despite that, he visits his father one last time before their third child is born. His Dad and he then travel back to when he was a kid, which would have changed his first 2 kids.
Suggested correction: This is not necessarily inconsistent with the movie's time travel logic. Since Tim goes back in time to visit his father and inside that particular time travel, they use time travel to go back to a day where Tim was a child. Then, they return back to the original time travel where they're playing ping pong. At that moment, both of Tim's kids were already born. So, when he returns from the ping pong scene, there's no change regarding his kids.
Also, paraphrasing the Dad, he said they aren't going to change anything. It is more like reliving a memory than changing the future to get what you want. The Dad couldn't go back to not smoke before his kids were born because that was major and would have changed the course of his life; walking a bit differently on a secluded beach that you walked on in your younger days (as long as you spent the same amount of time - presumably) would not alter the trajectory of one's life.
The slightest change in 1 second of being on the beach would absolutely affect his kids. A man produces 1500 new sperm every minute. Altering the timeline and delaying every event that is going to happen by literally 1 second would most definitely alter which exact sperm was used when conceiving both of his first two children.
Continuity mistake: When Theodore goes to Amy for comfort in her apartment, there's someone (or something), walking at the front door, but then not again in the next shot. Keep your eyes top right, it's very visible. (01:26:50)
Continuity mistake: In the scene where Grug is chasing after Guy, they both wind up stuck in a tar pit. After successfully escaping they are covered in tar and Grug even gets himself stuck to Guy. In the next scene everyone is running from the exploding ground up between the mountains and both Grug and Guy are completely clean and free of tar.
Other mistake: Sam draws an orange vest for Lockwood using a dark crayon. (01:10:45)
Plot hole: When Jake first meets Reggie, he tells Reggie that the Great Turkey told him everything about him. Later in the movie, when Reggie goes back in time and introduces himself as the Great Turkey to a young Jake, he only tells Jake to find the "Pardoned Turkey" but never said that the pardoned turkey's name was Reggie, so there's no way the adult Jake would know Reggie's name when they first meet.
Continuity mistake: When Sandy takes a taxi and goes to Diane's house, as he is arguing with her, the sweat pattern on his shirt changes several times as the scene switches from him to her and back.
Continuity mistake: When Walter Mitty is on the skateboard riding towards the Icelandic town, there is a shot of him riding along wearing Nike Frees, the camera then cuts to a close up of his shoes and the board, and the shoes in that shot have changed to Vans authentic.
Continuity mistake: When James Franco is talking about jizzing all over Danny McBride, the camera goes behind Seth Rogan and you can blatantly see him laughing, then milliseconds later when the camera moves, his face is serious. (00:57:00)
Continuity mistake: In the scene where Kenny feels he's been bit by a spider on his privates and run off the bus with everyone following after him. Kenny then pulls down his pants so they can look at it. Throughout these scenes, his pants are supposed to be pulled down. Right at the moment Kenny faints from the bite, you can see that his pants are pulled up and buttoned.
Continuity mistake: In the scene where Alan flirts with the store clerk, they share a lollipop. You can hear a "crunch" indicating that she chewed the lollipop. In the next shot, she takes the lollipop out of her mouth and it is still completely intact. (00:59:45)
Factual error: When Ron and Freddie have breakfast in the diner, Trivial Pursuit cards are seen on the table. The game was first sold in 1982, but the movie is set in 1980.
Plot hole: The premise of the movie is that a group of this man's genetic offspring have united to learn his identity. He receives a stack of the bios of those in the lawsuit. One of the children he visits is severely disabled in a nursing facility and would not have been capable of joining the lawsuit.
Continuity mistake: In the scene when Mike is at the school door lab. When he swipes the access card the door swings out. But when the campus police try to get in it is blocked from the inside, indicating the door opens inwards.
Suggested correction: If you look carefully, you will see, that those are actually two different doors, which even have hinges on different sides. There's some space between them in the entrance to the lab, it can be seen just before Mike enters.
Factual error: In the scene where the young Helen Goff is traveling by train with her family, it's obvious that an American engine and coaches have been used, instead of a Queensland Rail locomotive of the era. None of the QR locomotives had flared smokestacks like on the one seen in the movie. The coaches are also incorrect - as far as I know, none of the Queensland Rail wood coaches had clerestory roofs with a set of windows in them like seen in the movie. When Helen looks out the back of the train, it's also obvious that the tracks are spaced at 'standard gauge' (4' 8.5"). They should be closer together, as railways in Queensland are built to 3'6" gauge instead. There is also no such company as the 'Queensland Victoria Railway Co', as marked on the coaches, as all railways in Australia are state owned.