Revealing mistake: After Sid runs off with Buzz yelling, "To infinity and beyond," when Woody begs Sid's toys on behalf of Buzz and says, "There's a good toy...he's gonna be blown to bits...we gotta save him, but I need your help," in the next wideshot of the bedroom the green carpet's outer edge around the room is bright white below the brown baseboards - Pixar didn't digitally complete it with color.
Other mistake: While Sid's toys are working with Woody to get Scud out of the house, just as Hand-in-the-Box is holding the doorknob we can see the screw mounted on the latch's hasp below the loop - which really doesn't make any sense, but as Hand opens the door the screw has suddenly vanished from the hasp and is now properly mounted on the doorway's loop plate, where it's meant to be. If the screw were really mounted through the hasp, the door could not be opened.
Other mistake: There are six various bolts, locks, and latches on Sid's door above and below the doorknob, and some are in their locked positions when the door either opens or closes. For example, after Sid replaces the doll head with the pterodactyl head and calls Hannah, when the door opens we can see the dead bolt and slide latch are both slid out in their locked positions and yet Sid's able to open and shut the door, which is quite impossible.
Revealing mistake: When Woody grabs hold of Buzz and uses his "karate chop action" while they walk backwards to the open door, as Woody says, "Sorry guys, dinner's canceled," in the wideshot of all of Sid's toys pay attention to the chair and table at the right side of the screen. What we're supposed to be seeing is the swivel chair with four legs/wheels (and the red toolbox resting on the seat) that's positioned in front of the table's angled wood two-by-four legs. But we don't see that. What we do see is the swivel chair and table all blended together - the seat and legs of the chair are somehow behind both sets of table legs and the chair's backrest is in front of the table, which doesn't make any sense.
Continuity mistake: While Buzz sets out to prove he can fly he slides down the loop car track, and in the shot from his POV the world globe is missing from the top of the dresser beside the door.
Other mistake: During the scenes in Andy's room, when characters are standing near the window beside Andy's bed, and also on both the interior and exterior sides of the window behind the desk, we can see the same markings/scratches/chipped paint on their white lower sash rails, though the marks on the exterior side of the window behind the desk, are actually opposite from the other marks.
Continuity mistake: Before Woody uses the remote control to have RC push Buzz off the desk, there are red, yellow, and blue pushpins in an empty area of the bulletin board, but after RC hits the bulletin board, in the closeup of the pushpins falling off those colors have changed to green, red, and yellow, with the green pushpin remaining in the empty space, but when the bulletin board starts to fall over that green pushpin is gone and it's back to the red, yellow, and blue pushpins.
Continuity mistake: In Andy's room, the general ("generil") store box under the crib near the closet door has a cow illustration on its right side, but in the next few shots there's a drawing of two windows on that side of the box, and then it keeps switching between the cow and two windows in following shots.
Continuity mistake: After Sid tapes Buzz to the rocket, when the thunder and lightning occur there's a shot of the window in front of Sid, and the window pane molding with the two handles at the bottom of the lower window is missing. When Sid walks over to that window it's back.
Continuity mistake: In Sid's room, there's a lightbulb hanging over the table (which he turns on when he switches the doll's and pterodactyl's heads), and its electrical cord that hangs beside the lava lamp (filled with toy heads) vanishes and reappears a few times during the scenes there.
Continuity mistake: At the start, when Andy uses the remote control to slam RC (and Woody) into the "bank" box it's pushed under the crib with all of its flaps open, but when Andy takes Molly and leaves the room all of the "bank" box flaps are closed up.
Continuity mistake: After Woody tosses the string lights to Andy's toys at the window Mr. Potato Head hangs onto the end of it, but in the shot from behind Andy's toys when Woody's shaking Buzz's arm and imitating his voice, we see the outside of Sid's window and the string lights have vanished, then they reappear.
Continuity mistake: During the scenes in Andy's room, the light switch plate on the wall near the door vanishes and reappears in some shots.
Other mistake: At the gas station, right after Woody tells Buzz that he found a space ship, while they're talking under the motor oil display we can see Woody's reflection on Buzz's helmet, but the reflection is not backwards - note the word "oil" and Woody's badge, etc.
Continuity mistake: While Andy's falling asleep, when Potato Head and Rex pop out of the Eggman Mover's box it has "Andy's toys" written on one side and the adjacent side is solid - no openings, but when Woody opens this box in the moving truck, there are now open handle cutouts on the two adjacent sides to where "Andy's toys" is written.
Continuity mistake: The blue blanket in Molly's crib repeatedly vanishes and reappears within the same scenes, such as when the batteries are put back into the baby monitor Woody shouts for everyone to return to their positions, in the overhead shot of the room the blanket's gone, but is soon back in its place.
Revealing mistake: After the opening credits when Woody is on Andy's bed, right after Woody opens his eyes and lifts himself up, his left hand passes through his face.
Continuity mistake: When Sid runs out of his room with Buzz, the chair's in front of the dresser smack between the bed and wall, but when Babyface knocks out the morse code on the bed frame the chair should be seen but has vanished, and then it reappears where it should be, right beside the bed.
Continuity mistake: After Buzz knocks over the tool box onto Woody, in the overhead shot from behind Buzz as he looks down at the floor and also the closeup of the toolbox, the dumbbell's between the chair and bed, but when Sid grabs Buzz and runs off the dumbbell's moved to the other side of the chair, beside the wall and dresser.
Answer: Baby face taps RR TOYS COME OUT. Telling the other toys to come out from hiding. Pixar stated this in their Toy Story character overview.
But why "RR"?
"RR" is shorthand for "Message Received." Babyface is telling Woody that he understands Woody's problem and then taps out to the other toys to come out.