Dude, there is nothing more funny than watching a bunch of Ewoks bowing to C-3P0. Except perhaps when the run away in fear of his magic.
And if you carefully watch the scene when Threepio reveals that the Ewoks think he's a god, Luke is desperately trying not to start laughing. And when Threepio says that he's not programmed to impersonate a deity, Luke really struggles not to crack up.
When the gang is made "part of the tribe" one of the Ewoks gives Han a hug. Chewie gets multiple hugs, much to his dismay. Han tries to look on the bright side.
Han: Well, short help is better than no help at all.
Plus, some of the ways the Ewoks take out the Imperial troops. For instance, a speeder bike is lassooed by the steering vane and whirls around into a tree, the pilot screaming all the while.
Poor Threepio, no respect at all.
C-3PO: He says the scouts are going to show us the quickest way to the shield generator.
Han: Good. How far is it? Ask him.
(3PO turns to ask, Han pulls him back)
Han: We need some fresh supplies too.
(3PO turns again; Han pulls him back again)
Han: Try and get our weapons back.
Han: Hurry up, will ya? Haven't got all day!
And Han turns him around again as the camera cuts away.
Han: Great Chewie! Great! Always thinking with your stomach!
When Luke announces, "This is your last chance, Jabba. Free us...or die!" It just sounds like an empty, pathetic threat when he says it, even though he and his friends end up laying waste to Jabba's court.
[Leia whirls around Han and shoots the stormtroopers]
Han's reaction when Leia breaks the news about Luke being her brother. It's hilarious as his expression goes from "What the hell?" to "YES!!"
What really sells it, is you know he was thinking about that infamous kiss in Episode 5. His face was pretty much the same face everyone else had thinking about that kiss in hindsight.
Leia must realize this, which is why she kissed him.
Luke: 3PO, tell them if they don't do as you wish, you'll become angry and use your magic. C-3PO: But Master Luke, what magic? I couldn't possibly— Luke: Just tell them!
C-3PO: You see, Master Luke? They didn't believe me. Just as I said they wouldn't.
Luke uses the Force to make C-3PO float, making the Ewoks tremble in fear. But 3PO's reaction is much funnier.
Luke: Thanks, 3PO. C-3PO:(dazed) I never knew I had it in me.
The newly-added NOOOOOOOOOOOO! during the scene with the Emperor torturing Luke and Vader killing him for the Blu-Ray releases. Evidently Lucas didn't have enough confidence in his viewers to understand the desperate conflict within Vader through us looking at his emotionless mask and having the dramatic music play, and decided that we needed some kind of indication that Vader was going to kill Palpatine and not, say, lift him up to change a lightbulb.
In a deleted scene of the bunker on Endor, when the famous commander says You Rebel Scum!, in the deleted scene, Han mouths "Scum?"
Yoda: "When 900 years old you reach, look as good, you will not."
His reaction when Luke's message reveals that he's being gifted to Jabba is utterly priceless ("Artoo, you're playing the wrong message!").
Chewie and two other Ewoks swinging on a vine to hijack one of the Walkers. Chewie's Tarzan Yell sells it.
The battle above the sarlacc pit. Despite being outmatched and having a blind crewmember, the rebels manage to beat all of Jabba's fully-armed mercenaries by basically letting gravity take its course. That sarlacc must have been really happy!
Boba Fett, the bounty hunter that spent the majority of The Empire Strikes Back being set up as an arch-enemy to the non-Jedi characters, is beaten when a blind Han Solo bumps into him, setting off his jetpack which sends him crashing into a barge and dropping straight into the sarlacc's throat. Then comes the belch, just to seal his humiliation.
Yoda's death was tragic, but one funny moment in the midst of it. When Luke asks him if Darth Vader really is his father, rather than tell him at first, he insists he needs to rest. He was literally trying to die quicker rather than tell Luke.
In the middle of the Jabba's Palace sequence, for no apparent reason whatsoever the scene suddenly cuts to outside the place where a giant frog-like animal uses its tongue to lap up a smaller creature, and then lets out a large belch, and then the scene cuts back to inside the Palace.
Han tries to open the bunker door at Endor by fiddling with some wires. Han says "I think I got it. I got it!" Only to have a thicker door close over the preious one. Han looks at the wires with a face that says "God, I'm such an idiot!"