Early on when The Janitor first enters the kitchen and starts cleaning, he has a piece of tape on his cheek. He doesn't actually apply the tape to his face until after the ostrich fight, which happens shortly after he cleans the kitchen.
Kathy has a bandaged hand when she climbs the ladder, but the bandage disappears when she enters Willy's Wonderland.
When Liv explains Willy's Wonderland's backstory to The Janitor in the kitchen, she states that it opened in 1996 as the "brainchild" of Jerry Robert Willis. Later, when The Janitor is fighting Willy, Willy throws The Janitor into the Birthday Song button, and at the end of the song it says "serving families since 1984".
When the first two fall through the roof and land in the ball pit, the other three also fall through and land within feet of the first two. Yet on the roof, the others were standing 10-15 feet away from the first two.
The roof above the ball pit is undamaged after the teenagers fall through the roof. The ball pit is also missing debris from that fall when The Janitor lands in it.
At the end the Janitor is driving away from Willy's when an explosion can be seen reflected in his sunglasses. This is impossible as the explosion was behind his car.
After the choking of Siren Sara, The Janitor stands up and breaks his handcuffs. But as he stands up with his hands behind his back, it can be clearly seen that there are no handcuffs. The Janitor just holds his hands crossed behind his back.
Animatronic puppets would not spew oil when beaten. They are electronic. This was likely done for the 'blood' effect.
As Liv runs away after beating up Tito Turtle, breath can be seen coming from Evan's corpse.
Sheriff Lund never actually turns the steering wheel the entire time she is driving to Willy's with State Trooper Olson. Her hands move slightly a time or two, but she never actually moves the steering wheel to steer the car, revealing that the car is stationary the entire time.
"Springfield" is spelled "Springfeild" on one of the MISSING posters.
During the bathroom fight between the Janitor and Gus the Gorilla, the last stall has a pull door. When Gus throws the janitor into it, the door has become a push door.
When speaking with The Janitor, Liv says "They've said the same story to countless other over the years" instead of "others."
When the Sheriff is talking to the Deputy in a car, black cloth is clearly visible outside of the window.
Liv says they have to find a way into Willy's to save the janitor before burning the place down, but how to get in there is a problem. Instead of taking down pieces of wood covering the windows, and breaking the windows, she crawls through the a/c ducts to try to find him.