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.
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.
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)
Plot hole: When Tim takes his sister Kit Kat back in time, she gets a sudden brain change as she realises she's now going out with his friend and finds him attractive in the changed timeline. However, Tim has no idea anything's different in his life until he gets home and discovers his daughter has become a son.
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)
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.
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 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: 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: 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 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)
Continuity mistake: In the hotel, at Gagamel's room when Clumsy suddenly opens the food lid and bonks the room service guy. The lid falls at the right side of the door, but in the next shot, when Gagamel opens the door, the lids is on the left side. (00:55:55)
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.
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.
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.