Revealing mistake: When Captain Needa is killed by Darth Vader because they lost track of the Millennium Falcon, in the background, two guards come to take him away. You can clearly see the dead captain get up almost by himself. (01:10:50)
Revealing mistake: When Leia and the crew return to cloud city to rescue Luke from the scaffolding, watch very closely as Lando ascends up the lift, just after the top hatch opens from the overhead angle, you will see that Lando has been replaced with a G.I. Joe look-alike figurine. (01:55:10)
Revealing mistake: During the attack on the rebel base, after the headless AT-AT falls on the ground, another one shoots at the rebels. You can see the pyrotechnic charges where the impacts are. (00:33:05)
Revealing mistake: When Luke and Leia are watching the Millennium Falcon leave at the end of the movie, its light goes through Luke's arm. (01:56:25)
Revealing mistake: After the headless AT-AT begins to fall over, watch its back leg on the right side of the screen. You can see a broomstick being pushed up from under the set. It raises that foot up in order to ensure that the AT-AT falls to the left side of the screen. (00:33:00)
Revealing mistake: Right before Luke nicks Vader in the shoulder with his lightsaber, Vader cuts through a railing. There's a hole in the railing exactly where Vader apparently cuts it. Also Vader's lightsaber never comes into contact with the railing, yet it sparks. (01:50:15)
Revealing mistake: When Luke and Vader are fighting in Cloud City, there is something looking like tape wherever they hit something with their lightsabers. Maybe it's pyrotechnic charges?
Revealing mistake: After Chewbacca pulls R2-D2 away from the power socket, he runs away, and you can see white rubber soles under his feet. (01:43:15)
Revealing mistake: When Darth Vader meet Luke in the Cloud city, you can see the stick used to make the special effects before Vader starts his lightsaber. (01:41:05)
Revealing mistake: In Cloud City, Lando, Leia and Chewbacca are running to the Millennium Falcon, and when then they run into a door after Leia shoots a stormtrooper, a white rubber sole can be seen under one of Chewie's feet. (01:42:40)
Revealing mistake: Vader cuts off Luke's hand at the wrist. When Luke is holding on to the antennae-like assembly underneath Cloud City, in one shot, Mark Hamill bends his wrist, revealing the gimmick. (01:52:55)
Revealing mistake: In the first shot of Luke riding on Hoth, the tauntaun leaves no tracks in the snow. (00:02:50)
Revealing mistake: Right after Luke and Darth fight for the first time, Darth gets kicked off the Carbonite freezer. Then Luke jumps down to fight him again. After he jumps, you hear what sounds suspiciously like a trampoline. Then in the lower right screen, you can see Luke's head pop back up into frame. Widescreen Version only, although the sound is audible on the fullscreen version too.
Revealing mistake: When the medical droid tests Luke's mechanical hand at the end of the film, his thumb moves before the "muscle." (02:00:40)
Revealing mistake: In the original (not Special Edition): When the AT-ATs are attacking the Hoth base, they do a camera angle from inside Luke's cockpit. As his snowspeeder is passing through the legs of an AT-AT, part of the cockpit becomes translucent and you can slightly see the AT-AT through a metal bar.
Revealing mistake: When Luke is talking to Han over the comlink, there's a shot of Han riding a tauntaun. The animal leaves no tracks in the snow. (00:03:35)
Revealing mistake: After C-3PO gets shot, as Chewbacca walks over to the door, his right foot crushes one of the steps on a small set of stairs. (01:19:25)
Revealing mistake: In the shot where the Falcon is underneath the Star Destroyer, it is transparent and you can see the part of the Star Destroyer through it.
Revealing mistake: During the battle on Hoth, after Luke says: "Hobbie, you're still with me?", there's a shot of an AT-ST shooting at the rebel and after that, there a shot of an explosion behind them. You can see that the rebels are actually dummies in that shot.
Revealing mistake: If you closely when Vader cuts through the three poles at the end of the lightsaber duel, you can see that the saber never actually goes through the poles. (01:45:50)
Answer: Star Wars being for the young and the young at heart, Han and Leia's relationship unfolds in a deliberately childish manner that kids can relate to and adults will find comedic. Leia is irritated at herself for her attraction to Han, and certainly unamused that Han teases her over it, while at the same time he is not brave enough to admit his own feelings, either.
TonyPH