(at around 35 mins) The Tiffany doll's mole appears before she draws it on.
(at around 6 mins) In Child's Play 3 (1991), the entire left side of Chucky's face was removed by a scythe. When Chucky is sewn back together in this movie, though, it's the right side of his face that is stitched back on.
(at around 28 mins) After Tiffany gives Chucky the bridal doll, the rice she throws at him changes between shots.
I believe in the end cemetery sequence the front of a car is seen. Later the man gets out of the car. The car was seen in a previous shot chronologically before it was to be there.
(at around 6 mins) The arm that Tiffany gets out of the chest to stick on Chucky has one finger pointing while the others are closed. When it shows a shot of Chucky before cutting to David, we see that all the fingers are outstretched, yet it is not the type of hand where you can move the fingers manually.
(at around 1 mins) The flag in the beginning of the movie is improperly displayed. When hung on a wall, the Union (meaning the stars) is supposed to be in the flag's upper right corner, or the viewer's left.
Chucky stuffs a T-shirt into the fuel door on the right side but Norton's patrol car is a 1993 Chevrolet Caprice 9C1 and the fuel door is located behind the rear license plate.
(At around 50 minutes) David says that Jesse and Jade have been accused of being serial killers, and tells Jesse that the difference between mass murder and multiple murder is that mass murders happen "all at once." While this is true, serial murder is defined by at least a twenty-four "cooling off" period between murders. Since the murders occurred on the same night, the correct term would be killing spree.
The Chucky doll's body style changes throughout the movie. When he is sitting next to Tiffany in her trailer and when Damien picks him up, his legs remain in a seated position, much like a G.I. Joe, but when Damien throws him, he lays flat like his limbs are limp like a rag doll. However, considering that Charles Lee Ray is controlling the doll's body, it is plausible that he chose these positions himself because he is always part human, he is never all doll.
(at around 22 mins) When Tiffany drops Chucky into the playpen, it is obvious that the Chucky doll is switched off and inactive.
Tube that pumps out fake blood is briefly visible when Chucky pulls out Damien's lip ring as he's killing him.
Damien should be able to dart his head around to get Chucky off him to avoid being suffocated by the pillow.
(at around 35 mins) When the Tiffany doll finishes her makeover and lights a cigarette, we hear and see the flame, but she never actually flicked the lighter.
(at around 33 mins) The Heart of Damballa that Charles Lee Ray was supposedly wearing on the night he was gunned down wasn't actually in the original Child's Play (1988). The newspaper clipping Chucky shows to Tiffany is in the previous three movies but does not show the Heart of Damballa, and in the original where we see Ray gunned down, the amulet is nowhere to be found.
The voodoo magic in the first three films has strict rules Chucky must follow if he is to possess a new human body and leave his doll body. He only has a limited time frame to possess a new host before he is permanently trapped in his current one, and his next host has to be the first person he shared his secret with (Andy in the first two films, Tyler in the third). However, with this film, he explains to Tiffany that if they are to transfer their souls into human bodies, they must retrieve the Heart of the Damballa amulet from his corpse in Hackensack, New Jersey. This lore completely contradicts the rules established in the first three films, because if Chucky only needed the amulet to transfer his soul into a new body (which this film infers he knew about it the whole time since he was wearing it the night he died) then he could have simply retrieved it from his own corpse as soon as he possessed the Chucky doll and transferred his soul into the first person he could incapacitate. This means his efforts to possess Andy and Tyler were pointless. In fact, the amulet did not even exist in the canon of the first three films, as Dr. Death never mentioned it to Chucky in the first film.
Chucky's remains from Child's Play 3 are being held for evidence in a local New York State precinct. Child's Play 3, however, took place in Missouri as evidence by the vehicle license plates and local radio ads seen in the film. There is no reason given why this evidence was transferred across state lines, and especially to a local police department and not a federal one.
Chucky is placed in a play pen by Tiffany, who then secures the top so he can't get out. Chucky can not only easily slip between the bars, but given that he has enough strength to drag the bodies of fully grown adults, he should have been able to easily break the wooden bars apart.
There's no explanation as to why the doll parts would be stored somewhere or how Tiffany knew where they were.
(at around 56 mins) When Diane walks into Jade and Jesse's hotel room.
(at around 37 mins) When Jade and David are talking outside Jade's house while waiting for Jesse's van.
(at around 33 mins) Chucky tells Tiffany to open the "Voodoo for Dummies" book to chapter 6, page 217. Tiffany turns to page 217, however "Chapter 11" is clearly visible at the top of the page.
(at around 6 mins) When Tiffany recreates Chucky, she places one of his eyeballs in backwards.