Continuity mistake: Spot finds four other humanlike creatures and goes to them. Arlo is standing several feet in front of them. He begins to push some dirt by using his nose. A close-up then shows him using his nose to draw a circle around the five others but he is standing much too far away to be able to do this.
Plot hole: They have to invent Nitrotrinadium when they travel to the future because it was not invented yet, but was in the Russian drink in 2010, so should have already been available when they travel to the future.
Revealing mistake: When Krampus walks toward Max after he yells at him to give him his family back, wires are controlling Krampus' arm. (01:24:30)
Continuity mistake: When Shaggy and Scooby are approaching the Demon as he eats, it is shown that he is eating from a platter of hamburgers and french fries. Scooby and Shaggy bump into his table, knocking the food all on the floor. When Shaggy and Scooby quickly put all of the food back on the table, it now has french fries and hot dogs.
Continuity mistake: When the woman is eating the bread roll on the train, the end of the roll switches from uneaten to having bites taken out of it and back again.
Continuity mistake: After Brad gets the electric shock, his shirt is completely clean but few shots later he has some burn marks on it.
Continuity mistake: The getaway car changes from a Peugeot Partner (1996-2003) to a Citroen C3 Picasso (2013-2017). (01:35:30 - 01:36:05)
Continuity mistake: In the early scene, when Maura is talking to the man in the corner, that she thinks is homeless, she stands up and has a green bag on her shoulder. When she asks for the sunscreen back, there is no sign of her bag. Then it's back on her shoulder.
Continuity mistake: When Jesse Eisenberg seeks shelter at John Leguizamo's house, John Leguizamo pulls a gun on him. Jesse Eisenberg grabs the gun from John Leguizamo and in the close up of this action it's a completely different gun. (00:40:55)
Visible crew/equipment: When Bryson and Katz are getting onto the Greyhound bus, a guy in a fluorescent jacket can be seen holding traffic up in the distance whilst the scene is filmed.
Continuity mistake: When Bianca takes Wes to the "thinking rock", as they talk and her hands are in her lap, her hair moves from over her left ear to behind her left ear and back, twice.
Continuity mistake: The guys pass 3 women walking on the sidewalk just before the Ciel pulls up at the hotel to visit Travis. 2 of these women are in the next shot where Vinnie and Eric get out of the car and walk into the hotel. The tall one in a floral dress walks away from the camera and stands to one side, and the blonde wearing the black top and spotted shorts is chatting in the background. (01:06:05 - 01:06:55)
Revealing mistake: In the Senior Citizen bus tour scene, just when the bus stops and almost hits the piece of construction equipment, Sofia Vergara is fixing her handcuffs. She adjusts them because one has visibly fallen off her wrist.
Visible crew/equipment: When Davis comes out from the train with the headphones on in the subway just before starting to dance, a cameraman filming the scene can be briefly seen reflected on the train door's glass. (01:08:00)
Revealing mistake: When Rachel has a red turban on and is supposed to be bald, you can see her hair under the turban.
Continuity mistake: Lotte is in her room looking at the checklist for the parade. The size and angle of the quill pen change every time there's a cut. (00:14:40)
Continuity mistake: After Liz and Bev tell Bill that they can't cancel the show, they are helping him put his suit jacket on. Dimitri behind him is using a sticky roller thing to get hairs off the jacket and is down on his back. After Bev mentions the weather issues the camera angle changes and suddenly Dimitri has the roller up on his shoulder.
Revealing mistake: At the cocktail party in his honor, Rita Richards introduces herself. Joaquin Phoenix's scotch is in a transparent plastic cup, and you notice what happens in most movies, here with particular clarity; when he brings it to his mouth, he does not take even a sip, but just pretends. (00:06:05)