In Miss Congeniality, Cheryl beats Gracie with the rose bouquet, and the petals fall off. A few seconds later, the red petals magically reappear.
In Harry Potter and the Chamber of Secrets, you can visibly see a cameraman in the shot during Harry and Draco’s dueling scene.
In Hitch, Will Smith’s character has an allergic reaction, and only one side of his face swells up. Later on in the night, the swelling switches to the opposite side.
In Soul Surfer, they wrapped green tape around AnnaSophia Robb’s arm to digitally remove it from the movie, but in the trailer you can see where they forgot to edit it out.
In Return of the King, Frodo gets caught in Shelob’s webs. Sam finds him and presumes he’s dead, but throughout the scene Frodo’s eyes go from open, to closed, and back to open again.
In Ocean’s Eleven, Brad Pitt’s shrimp cocktail container changes from a glass to a plate, and then back to a glass again.
And, of course, in American Sniper, they substituted a real baby for a literal doll. You can even see Bradley Cooper move the doll’s hand with his finger, to make it appear more real.
Jurassic Park: The Helping Hand
Fans of Steven Spielberg’s Jurassic Park likely remember the scene in the film in which giant velociraptors chase Lex and Tim Murphy through the kitchen. However, what most viewers probably didn’t pick up on was that as the first dinosaur walks through the kitchen entrance, there is a brief period in which you can see the hand of one of the crew members holding onto the beast to keep it steady.
Spider-Man: The “Broken” Lamp
In Spider-Man (2002), there is a scene at the beginning of the movie in which Peter Parker is first discovering his powers and, in the process of testing them, accidentally breaks a lamp in his room. However, when his aunt comes in to see what’s causing all the noise, the lamp has miraculously fixed itself and is back in its former resting place.