Goofs

The glass Bill uses to cut everyone's hands doesn't stay bloody for each character despite him never wiping it off.

Bill's wristwatch switches from the right hand to the left hand through several consecutive shots.

When Eddie leaves Ben's house to walk down Neibolt Street, he is wearing completely different clothes.

When Beverly Marsh first meets Ben Hanscom, she signs his empty signature book. When she does this, she removes the cap of her pen with her mouth, and holds the cap in her teeth while writing. The camera switches between Beverly and Ben several times while she is writing, sometimes the cap can be seen in her mouth, but other times it is missing.

The inside and outside views of the windows of Billy's bedroom don't match. This is plainly evident at the beginning of the film. From the inside they are standard windows, but from the outside they are bay windows.

Police cars are shown with red and blue lights. Police cars in Maine only display blue lights.

Ed has a broken arm with a cast on it. Ed accompanies his friends into the sewer were there is water everywhere. Even falling into the water which would destroy the arm cast but it seems undamaged in the end.

A large container train is shown in the background with modern logo Hapag-Lloyd containers. While double-stacked container trains were introduced in North America in the early eighties they were not common in 1989 because of low bridges and tunnels that had to be replaced to accommodate them.

Just because they were not common, does not mean they did not exist, thus this not a goof, nor is it an anachronism.

While Pennywise is speaking to Eddie just after chasing him in the form of a leper, he raises his upside down triangle of red balloons. While cutting to Eddie and then back to Pennywise, you can clearly see Pennywise holding the string attached to the balloons but in the final shots of him speaking, the string is nowhere to be found; as if the balloons had magically disappeared. However, this isn't the case, as you hear and partially see all of the balloons popping after Pennywise has finished talking.

The hole in the floor that Eddie fell through is gone when Bill and Richie come out of the room with the mattress. This is most likely due to the fact that Pennywise created the hole in order to stop Eddie from getting to Bill and Richie. He probably returned the floor to its original state after Eddie fell through so that Bill and Richie won't know what happened to him, and increase their fear, due to them not knowing where Eddie is or what happened to him.

When the fight between Beverly and her father breaks out, she kicks him in the privates more than once and he goes down but miraculously gets up again. He wouldn't have been able to get up that quickly after being kicked like that.

In situations such as fights, the body releases adrenaline which can allow people to overcome pain.

When Richie and Bill are upstairs in the Neibolt house trying to get to Eddie, they choose the door "Not Scary at All." When they open the door, a female voice asks "Where's my shoe?" Bill reaches for and turns on a light. This shouldn't have been possible because the house would not have working electricity, however, given the fact the entire house can be manipulated in any way Pennywise wants, the electricity is perfectly explainable.

When Stanley is in the synagogue reading out loud from a book in Hebrew, he is clearly holding the book upside down, revealing the actor cannot actually read Hebrew.

During the rock fight, the Losers hit several of the bullies with very large rocks, but they simply bounce off without the bullies even flinching.

When Ed breaks his arm, his forearm is suddenly longer than it's supposed to be.

When Ben encounters the three bullies and Henry, and they assault him on the bridge, the punch that Henry throws never lands anywhere near Ben's face.

In the pharmacy, to the left, each shelf has price tags. On the right, none of the medical items have prices.

When Bill visits Georgie's room he picks up a green Lego turtle which later breaks on the floor. Green Lego brick other than plates for building structures on, or 1/3x1 plates did not exist in 1988/1989. Lego's reasoning behind this is they didn't want children building tanks from the bricks. The green 2x4 bricks shown were introduced in 1996 and the color lime (aka bright yellowish green) was introduced in 2001.

In the first pharmacy scene, the beauty products on the shelves have modern day packaging. Most noticeable are the Dial and Ivory soaps and the Olay products.

In one of the pharmacy scenes, a dome style security camera can be seen on the ceiling. This style of camera was not in use in 1989.

The TV shown in the background in the Denbrough house is actually a Toshiba TV from the early 2000's. Also, the RCA VCR that is on top of the TV in the Kaspbrak house is from the late 90s/early 2000's.

One of the televisions at the start of the film in one of the houses is a silver Sony CRT that was typical of the early 2000s rather than the late 1980s.

Derry, Maine is in the USA, however, a war memorial contains the line "For king and country", revealing the filming location in Canada.

After the rock fight, when the Losers are walking, a train can be seen in the background. One of the freight cars has a logo of Canadian Tire, a Canadian hardware store. The film was shot in Ontario, Canada.

The large, open storm drain shown in the film's opening scenes is not common in Maine and is more commonly seen in the Western USA.

During the rock fight scene, Richie is clearly seen getting hit by a rock in the head. Yet, in the reminder of the movie Richie is not shown to have any sign of a head injury and remains undamaged throughout the movie.