Continuity mistake: When Holland shows the bartender the dollar bill in the shape of a shirt, he is smoking a cigarette before he takes the cigarette out of his mouth. Holland mentions to the bartender that he made it himself, with nothing in his mouth, but in the next shot, the cigarette is suddenly back. (00:09:45)
Continuity mistake: Russell Crowe is dunked head and torso in a pool, immediately gives chase to Blueface, but he's basically dry when reaches Holly. Later in the movie it's even worse, since Ryan Gosling has a near-death experience falling in a pool, but he runs as normal, only slightly moist in the hair (and even pulls out a cigarette and lights it later by the time the cops arrive).
Continuity mistake: John Boy draws the knife and makes his generous 'offer'. Cuts back to the Nice Guys who are driving fast; the Mercedes, as dirty as it is, is still perfectly intact with both sets of headlights working and the hood ornament. The front section was damaged when March fell asleep at the wheel earlier, and the car is again damaged when they pull over in the driveway. (01:24:10)
Continuity mistake: Jessica is on the phone and asks the person on the line "Richard something? Yeah." Holly in the background just puts her hand one one of the nearest cards, but at the cut she's moving her hand back from the top of one of her solitaire lines. (01:22:00)
Continuity mistake: When Russell Crowe says in front of the hotel "She's meeting somebody", the steering wheel is turned in a different way than you see later as he turns the wheel straight. (01:07:40)
Continuity mistake: March realises he's sitting next to Robert Downey Jr. with a fake beard and quite dead. Notice his necklace, worn above the tanktop. In the rest of the scene the chain is above or below the shirt, randomly. (00:44:30)
Continuity mistake: When Chet tells March "make a left here", he's pointing with his left hand. In the next shot his left arm is in a different position and he's pointing with his right hand. Moments later when he points at the house he lowers his arm but he's again pointing in the next shot that shows it is burnt down, and again even more blatantly after a close-up where his arm is all the way down. (00:29:20)
Continuity mistake: The two protagonists struck a deal to cooperate. Jackson is saying aloud the caption of a photo from a newspaper, holding it by the length while they walk in a longshot. At the cut he's holding the newspaper by the shorter side, and back to the longer side when they get back to the wider angle. (00:26:40)
Continuity mistake: When Haley asks "Why not go straight to the police", Amelia has just a bit of her hair in front of her left shoulder, a greater portion of it in the next shot. (01:14:55)
Continuity mistake: When the older dude tells the protagonists "They can't talk to you, man, they're dead", his pen points down in the wide shot, up in the close-up. (00:28:10)
Continuity mistake: When Mrs. Glenn shouts at March for cussing, she points at him with her left hand. Next shot and she's pointing with the right. (01:31:10)
Continuity mistake: When March says "Tally! Oh my God, you look incredible", he opens his arms, which are still firmly down his sides in the next shot. (01:34:55)
Continuity mistake: When the Nice Guys in the ending mention Lynda Carter, they are holding their smokes in entirely different ways between shot and reverse. (01:50:25)
Continuity mistake: When at the end of the movie Kim Basinger sits with the Nice Guys (well, back-to-back with them, kinda), March is already wearing the sunglasses that he puts on when she says "Boys, boys." (01:47:15)
Continuity mistake: John Boy throws his jacket in the street, but in the brief shot where Jackson tackles him he's still wearing it. (01:44:55)
Continuity mistake: When the older guy falls back and tries to drag Holly with him, she wiggles free leaning towards him, but in the reverse shot she's rotating the other way. (01:41:05)
Continuity mistake: Holly throws coffee on Tally, but her face and dress are clean a moment later. (01:37:30)
Continuity mistake: Mrs. Glenn drops by to chat about the case; during the scene, her large square necklace is under or above her dress, randomly. (01:30:15)
Continuity mistake: After the encounter with John Boy, March asks Perry a question. He says "They havent', and they are not going to." The sentence spans across two shots, with a visible gap in continuity in the way Russell Crowe puts his sunglasses on. (01:28:25)
Continuity mistake: There's a brief cut to Ryan Gosling saying the line "Okay, so it's like Jack the Ripper and then your mom, basically." Amelie doesn't move, but her hair changes position completely. (01:16:05)
