Continuity mistake: In the library scene Indy discovers the "X" high up on the balcony. The X is green with a grey background. When he breaks the tile to find the tomb the X has become a faint outline on the floor. (00:27:40 - 00:28:45)
Continuity mistake: The batting order in the one-game playoff is Taylor-Dorn-Cerrano (as seen in the 7th), with Hayes batting before Taylor (as seen in the 9th). Cerrano hits the homer with two outs in the 7th, and Hayes is shown batting with nobody on, and two outs in the 9th. If they faced the minimum, Hayes would've been up with only one out (#5 batter gets the third out in the 7th, 6-7-8 batters get out in the 8th, and the #9 batter gets one out before Hayes). There's no way they could've gone through the line-up again without scoring a run. The furthest they could've gotten was the #8 batter (two spots before the leadoff Hayes) coming to bat in the 9th with two outs and nobody on. (01:23:30)
Continuity mistake: Notice Marty's hair in the scene when he's playing "Johnny B. Goode." It's quite larger than when he says, some seconds later, "I guess that you're not ready for it yet." That's because when he says that, it's a recycled shot from the original BTTF, whereas most shots showing he's playing the guitar are newly made for BTTF2. However, Marty's hair is considerably longer in the new shots.
Continuity mistake: When Spock, wearing rocket boots, is in the turboshaft carrying Kirk and McCoy on either arm, he fires the booster rockets, thus propelling the three of them up the turboshaft. If you watch carefully, the deck numbers in the background as they rise upwards go as follows: 35, 52, 64, back to 52, 77, 78, and then 78 again! Not content with one goof, Kirk and McCoy can quite clearly be seen with their feet dangling in mid air, not on Spock's boots. They aren't exactly clinging to him either, more like leaning against him. Surely Kirk and McCoy would be unable to hold onto him!
Continuity mistake: At the end of the movie, when Riggs is in the cargo area, a gunman shoots at him, he rolls and starts emptying the clip into him - you see the bullet holes in the gunman. But as Riggs is face to face with the gunman, the holes disappear.
Continuity mistake: During the first car ride scene Harry is spitting the seeds out the window. One of the shots shown of the car from the outside shows the window still up after he has rolled it down.
Continuity mistake: In the scene where Ouiser sits and lets out a belch, if you look in the mirror, you can catch her laughing.
Continuity mistake: Early in the film Bud throws his wedding ring down the latrine and then retrieves it with his right hand so it is covered with the blue disinfectant. In a (much) later scene, Bud has a blue right hand, despite not having had one in the intervening period. (01:44:48)
Continuity mistake: When Uncle Lewis and Aunt Bethany have just arrived and Aunt Bethany says, "Oh dear, did I break wind?" Ellen helps Aunt Bethany fully remove her coat. Seconds later, within the same scene, Ellen is still helping Bethany off with her coat. (01:02:45)
Continuity mistake: When Philip surprises Alex and Corrine undressing in the living room, Corrine throws her panties in the air and they land on Philips' head. Philip pulls the panties off his head and throws them down. After a quick cut to the surprised Alex and Corrine, the camera cuts back to Phillip with the panties magically back on his head.
Continuity mistake: During the first battle in the woods, the Union Regiment levels their un-bayonetted weapons and fires a volley at the Confederates. About 3 seconds later, without the order having been given, they are in hand to hand combat with bayonets fixed.
Continuity mistake: When Stallone stops the bad guys in the semi full of cocaine, they fly through a windshield that is apparently made of plate glass, and not the safety glass found on almost every other vehicle windshield on earth.
Continuity mistake: When Beck meets Webly on Christmas Day, Webly takes his glasses off and throws them on the desk, but in the next shot (from behind) he is still wearing them. (00:16:50)
Continuity mistake: When Lloyd calls Diane's house for the first time to ask her out, he gives her father his phone number as 555-1342 (several times), but later when Diane is reading her list of messages, Lloyd's number is listed as 555-2342. (00:12:40 - 00:15:50)