When Jeff grabs the box of flashbulbs, all four can be seen in the box, but when he backs up more, there are only two left.
The amount of brandy in the detective's glass increases between shots.
When Thorwald returns home from one of his trips out in the rain lugging his suitcase, the camera (from Jeff's point of view) pans from a glimpse of Thorwald on the street, across Miss Torso's apartment where she is preparing to go to bed, to the second floor hallway where Thorwald is walking toward his apartment. This observed action takes only a few seconds - an impossibly short time frame for Thorwald to have entered his building through its front door, walked over to the stairwell, climbed the stairs to the second floor and then be seen walking along the second floor hallway.
The location and angle of the shadows of the "sun" are in the same place in the morning and at night.
Lisa takes the binoculars away from Jeff and wraps the neck cord around them before putting them on a small cupboard. When Jeff picks up the binoculars later, the neck cord is no longer wrapped around them.
It's possible the annual phone directory was published during the first few months of Thorwald's lease.
Jeff wheels himself over to the window and bumps his broken leg against the wall below the window, yet he doesn't grimace at all.
A broken leg in a cast for seven weeks (and just a week from coming off) is scarcely more sensitive to such bumps than an uninjured leg.
When Lisa and Jeff are discussing "rear window ethics",Grace Kelly noticeably stumbles her line "Jeff, you know if someone came in here they wouldn't believe what they'd s...see." This should not be considered an error as people misspeak and stutter in real life all the time.
Miss Lonelyhearts lays out a handful of pills on a nightstand. The pills should be the size of ants given how far Jefferies from Miss Lonelyheart's apartment. Viewers can see that the red pills are the size of horse tranquilizers. Typical humans would have a hard time swallowing just one pill.
Not only is it a fictional drug that could really have any size, some real life pills are indeed surprisingly large. This is where the joke about a pill being a "horse pill" came from to begin with.
An obviously accomplished staffer of the 21 Club brings the couple their dinner and wine, and Lisa is purportedly top tier society, yet they're chilling red wine.
This is incorrect; Lisa says they're drinking a Montrachet, which is a white wine.
The helicopter seen near the start is obviously a composite, as there is camera shake in the copter footage.
As the camera pushes in for a closeup of Lisa (her suspicions suddenly aroused), if the viewer listens closely, the creak of the camera as it dollies toward her can be heard.
As Lisa is in the kitchen preparing the brandy for Doyle and Jeff, her silhouette can be seen on the ceiling. The silhouette is of Grace Kelly with her hair down, though moments later when she emerges with the warmed brandy, her hair is swept up in a French Twist.
When Miss Lonelyhearts and the songwriter are talking about his record in his apartment, the dubbed-in dialogue doesn't sync with the picture, even to the extent of Miss Lonelyhearts being heard to say "I can't tell you what this music has meant to me," while her mouth isn't moving.
When Stella goes to the door saying she's going to find out the name of the freight carrier that is taking off with the trunk, someone who sounds nothing like James Stewart has dubbed him with the peculiar sounding line "I'll keep an eye on the alley." Stewart is holding the binoculars over his mouth, but he's not moving his lips. Prior to that, when he says "Don't do anything foolish", his lips are still moving after the audio is heard.
While Lisa and Stella are digging up the flowers, the pianist is shown playing with other musicians. When the harmonica players starts to play, a saxophone is heard although none is visible. The harmonica is subsequently heard also.
After Lisa sees Thorwald tie up the trunk and the camera dollies forward to a close up, there are creaks from the floorboards and footsteps heard from the camera crew.
When Doyle is on the phone to a colleague and before Lisa comes out of the kitchen, the shadow of a camera crew member is visible on wall by the kitchen window.
When Stella tells Jeff that Thorwald's blinds are "up now", Jeff spins around and moves back with Stella into the shadowed part of his apartment telling her to "Get back. He'll see you". But immediately afterwords, while Thorwald is looking out of his window, Jeff moves back into the bright sunlight.
After Doyle shuts down Jeff and Lisa's arguments that Thorwald killed his wife, Doyle suggests they have a "nice friendly drink or two" and then follows that up with "How about that drink?" He does this even as he is holding a glass with brandy in it.