If Buzz does not believe himself to be a toy, and in fact a real space ranger, why would he freeze around humans like the other toys do?
When Buzz and Woody are trying to get back into the moving van, Woody opens the boxes of Andy's toys in search of R.C. All the toys react to having the box opened by shielding their eyes and commenting on it. However there was no guarantee that it was a toy opening the box and therefore they could have just revealed their ability to talk/move to either a removal man or any member of Andy's family.
When Andy puts Woody and Buzz on the desk, there is no Magic 8 Ball - but a second later the Magic 8 Ball appears right next to Woody.
Buzz's wings should have been caught on the car track loop when he demonstrates how he flies.
When the RC car runs out of batteries, Buzz drops the remote control. That remote disappears from the street when Woody lights the rocket.
Sarge's binoculars are made of opaque plastic. He shouldn't have been able to see through them, but this movie's toy logic is arbitrary.
Throughout the film, an important plot point in the film is that Andy's family is moving within days. This fact is mentioned when Woody tells the toys that there is one week left before moving day and there are repeated mentions of the moving in progress throughout the film which takes place over at least a few days to a week. Yet, during the "Strange Things Are Happening To Me" sequence in which Woody sees Buzz becoming the dominant toy in Andy's room, Andy's mom has gone through the trouble of changing the wallpaper in Andy's room from cowboy-themed to spaceman-themed. Generally, there would be no point in such a dramatic decoration change if the family is planning to move out of the home within days of Andy getting Buzz for his birthday.
Rex combines anatomical elements of Tyrannosaurus Rex, Giganotosaurus, and other dinosaur kinds. He's a generic caricature for toy marketing, not a scientific exhibit.
The burn mark on Woody's forehead disappears.
The lever that lowers the ramp on the moving truck changes from black to red.
The license plate on Andy's mother's car reads "A 111" on the front but "A 113" on the rear - this is an in-joke (see trivia).
In some scenes, the mother's minivan is shown to have a sunroof; in others, there is no sunroof.
When "Legs" and "Ducky" remove the porch light fixture to ring the doorbell for the "escape", they pull the fixture up through the hole in the ceiling. They are also able to lower it back through afterward. You would be unable to do that with a real fixture of that sort, as housing would be bigger than the hole so it could be attached to it.
The bulbs in the string of Christmas lights disappear for a while.
The length of "lasso" of lights change length from scene to scene:
When Woody is a regular toy, his mouth alternates between closed and smiling to partially open.
While planning the rescue of Buzz from the rocket, the clock on Sid's wall jumps from 6:35 to 10:00 to 3:10.
Near the beginning, when Woody is on the bed, a rendering error occurs when, as he gets up, his left hand passes through his face.
During the birthday party, the toys use the wrong parts of the baby monitor to communicate. Sarge is using the receiver and Woody is using the transmitter; it should be the other way around.
When Sarge looks through his binoculars for the first time, they are upside down.
When all the toys are amazed at Buzz Lightyear's laser, Woody comments that it is only a "light bulb that blinks". However, whenever Buzz uses his laser, the light is concentrated in a single red dot, indicating that it is in fact a laser (normal light diverges; think of a flashlight beam getting larger as you move farther away).
The bug smear on Buzz's visor appears and disappears between shots during his fight with Woody at the gas station.
In the gas station, Woody and Buzz get on the Pizza truck which has amber rear side markers. However, US-Spec requires vehicles have red rear side markers; amber rear side markers are Euro-Spec.
The ramp disappears when RC is tossed into the truck, and then it reappears when Buzz and Woody fly past.
After Buzz tackles Woody on Andy's bed (to protect him from the strange lifeforms), the laser on his forearm is activated without him pushing the button on his bicep - during the rest of the movie, he pushes the button on his bicep to activate the laser.
In the beginning of the movie when Andy takes his baby sister out of the crib, he lowers the crib side to get her out. He does not put the side back up, but in the next shot the crib side is back up.
The "Improvised Interrogation Handbook" that Woody hides under is visible next to him while he is trapped under the crate but disappears when Buzz begins to help. It's clearly gone in the close-up scene in which Woody begins to push the crate.
After Buzz tackles Woody on Andy's bed, and Buzz meets the rest of the toys in Andy's room, there is a wide shot of the bed. In this shot, the little light that is Buzz's "laser" (on his right forearm) is missing.
While preparing to escape from Sid's room, several of the locks on Sid's door are still closed/locked in one shot, but are unlocked when the escape begins.
Several toys used in the movie are not to scale with the other toys. For instance, "Mike" is much larger than a Mr. Potato Head.
When Woody or Buzz look through the binoculars (Lenny), the view is shown to be the typical double image even though they can only look through one opening. The image should be like looking through a telescope.
The book in the crate where Woody is trapped under is titled TM 31-210, Improvised Interrogation Handbook. The actual title of the TM is Improvsed Munitions Handbook.
At the gas station, the truck pulls up and Buzz jumps out of the way and Woody goes limp and falls, the truck's back tire is shown nearly running over Woody's face which means that the front tire had to have run Woody over.
In the film Mr. Potato Head's eyes and feet are separated. His eyes have a separate hole for each and his feet can move separately. An actual Mr. Potato Head's eyes are connected together and only have one hole they fit into. The feet are also connected together which means he should not actually be walking in the movie but hopping or walking like the army men do.
Continuously during the staff meeting in the beginning of the movie, the spokes on the painted wheels of the toy chest move from the left dot to the right dot and back.
In the scene when the troops are warning the toys that Andy is coming up to the room, it shows Woody standing next to the baby monitor. It then shows a "panned out" scene of all the toys running to find a place to hide, and the monitor is no longer there. Next scene shows Woody standing next to the monitor again.
"Legs" and "Ducky" go into the air vent of Sid's house at the beginning of the rescue, but when they go to the garden they come out the drain pipe which would be attached to the outside of the roof not coming from inside the house anywhere near the air vent.
After buzz asks Woody if he wants to complain to star command, the height of Buzz's helmet relative to Woody changes as the camera faces Woody. When the camera cuts back to Buzz, he is once again at sitting height.
When Andy leaves his bedroom on the moving day, he is wearing a green T-shirt and blue shorts. Later in the car he is wearing a blue T-shirt and brown shorts.
Mr. Spell's vacuum fluorescent display or VFD has vertical and horizontal lines only, not diagonal. In some scenes we see words displayed that would not be possible with this type of VFD. For example: "YOU'RE WELCOME". This type of VFD cannot display a capital "R".
When Buzz and Woody are in the gas station, the close up shot of Woody shows the moon over his right shoulder as a crescent shaped like the letter "C", but backwards as if in a mirror. When the shot changes to Buzz, the moon's reflection in his helmet is also shaped like a backward facing "C" instead of a forwards facing one.
Toward the end of the movie when Woody opens the moving van door and is hanging on it you can clearly see in the background Scud trying to get Buzz from underneath the car, but right after Woody spots the box he needs to look in we are shown a scene of Scud struggling with Buzz who is at this point thrown under the car.
Prior to Buzz being knocked out the window by the red desk lamp, in successive shots, the desk lamp repeatedly moves from the left-hand side of the desk to the right. Also, the globe hits it and knocks it in a full circle, yet it was never far enough from the wall to spin entirely around (as it needs to in order to knock Buzz out the window) until the moment before the globe hit it.
In Sid's house, the BB gun target's numbers are backwards. This can't be a mirror image because "Sheriff" is written correctly on Woody's badge in the same scene.
When Sid puts the Alien Toy on Scud's nose, look at Scud's chest as he breathes. His chest seems to be passing through his legs. This is a rendering error.
When Woody pulls Buzz out from under his ship and rebukes him, his eyes actually point over Buzz's head instead of at his face. In the next shot where Woody asks if he wants to do things the hard way, they are actually looking straight past each other.
As Woody first gets up, the spurs on his left boot pass into the bed sheets.
When Buzz first presses one of his buttons, a little fanfare plays before his voice calls out, "Buzz Lightyear to the rescue!" Later, while Buzz and Woody are fighting under the van at the gas station, the button does not play the fanfare.
The rain droplets on the window often remain in place even when more drops fall on them, instead of merging with them.
When Bo looks through Lenny the Binoculars, her elbows partially clip through her dress.
When the toys are making their escape, after Ducky and Legs ring the doorbell, Hannah opens the door when and Ducky is sitting still on the floor and Hannah doesn't even notice that he is there. But she would have as he is right in front of her.
Despite falling from the top of Sid's stairs Buzz only breaks an arm. Buzz should really had his glass helmet smashed and suffer other forms of damage from that height.
When RC hits the corkboard, the pins stick into the desk. When the globe rolls after Buzz, the pins are gone.
When Woody prepares to send out the troops and speaks with the sergeant, the sergeant has a pistol in his right hand. In the next shot it is gone.
At the gas station, the reflection of the moon in Buzz's helmet is illuminated on the right side, which implies a real moon illuminated on the left side. Yet when we look at the moon over Buzz's shoulder we see that it's illuminated on the right.
When Hannah sets down Buzz's arm, which is in turn holding the teapot, the teapot is pointing towards Buzz. When Woody enters the room it is now pointing away from Buzz.
When the toy soldiers are parachuting downstairs we see their parachutes, but in the next scene when the rest of the toy soldiers slide down on the jump rope the parachutes are gone.
As the aliens tell Buzz about their "master", Woody can be seen behind them, both hands on the rim of the exit chute. In the very next shot, Woody has his left hand on his forehead.
Buzz's laser is located on top of his forearm. However, when he lifts and holds onto his foot to show the others that Andy inscribed his name, his laser is on his inner arm.
While the staff meeting When Mr. Potato Head does the Kiss-My-Ass joke, a rendering error occurs when he reaches to his mouth his hands passes through his mouth.
When Woody is being pulled away from the truck by Scud, the distinct sound is heard of something, presumably Woody, tearing. Yet Woody is not torn for the rest of the movie.
Right after Hamm announces "Birthday guests at 3 o'clock!", there is a brief shot of some of the toys reacting in horror. In this shot, Mr. Spell can be seen and his display flashes "You're Welcome" for 2 frames and goes back to a blank screen. Just over a minute earlier in the film, Mr. Spell displays "You're Welcome" after Woody comments on the success of his plastic corrosion awareness meeting.
When Woody grabs the match from his holster, when seen at a slightly slower speed, he doesn't actually grabs it, it actually jumps into his hand.
When Hamm uses the remote to turn off the TV, he is on the table top with Rex in front of the TV, but when the TV turns off, the table top is reflected on the blank TV screen and Hamm and Rex are not there.
After a car passes by, extinguishing the fumes, the match disappears when Woody crouches to cry without ever seeing him put it down.
When Buzz is trying to prove that he can fly, he jumps from one of the bed legs. Therefore there is no way he could reach the ceiling without getting additional speed (which he gets only after reaching the ceiling).
When Woody goes into Hannah's room to retrieve Buzz, the coil of Christmas lights are right next to the door. When they come out, the coil is missing. It is there again when Woody picks it up to go back to Sid's room.
The coiled "lasso" of Christmas lights that was outside Hannah's bedroom disappears when Woody and Buzz walk out from Hannah's bedroom. It reappears again as much smaller coil and right by the door in the next shot showing Hannah's doorway.
When Buzz is sitting on the floor of Sid's room, he is wearing his "Mrs. Nesbitt" apron. As Sid's toys converge on Buzz, the apron is gone but is tossed away an instant later while the toys work on him.
When Andy's mom tells him to bring Molly downstairs, some of the fingers on Andy's left hand briefly clip through the chair next to him.