Please do. 
Heh. Remember during “Welcome to the Dollhouse” when the little sister is missing and all they find is her tutu? My father and I crack up (it’s a dark comedy and everything will be fine in the end) at the dark humor of it but you should have seen the people around us. They were treating it as suspense that could actually turn out horrible and were looking at us like we were monsters.
After Attack of the Clones, the theater was leaving through the lobby and this very gay-sounding guy says to his friend, “I’m sorry, but Yoda turned it out!” People laughed.
Back in college, I knew a guy who claimed to have stood up at the beginning of Imagine and yelled out “I hear he dies in the end.”
When I saw the first Michael Keaton Batman movie there were a lot of cool moments in the movie like when the batplane flies in front of the moon and looks like the bat signal when the audience cheered or clapped. I definitely find that the movie giong experienced is heightened if the audience gets into it. There was a lot of cheering during the second round of Star War movies, and Harry Potter and LOTR movies, and of course, Serenity.
Ok so we shouldn’t laugh at comedic movies either because the actors have no way of knowing we thought they were funny? Clapping and cheering aren’t about giving feedback to the makers of the movie. It’s about expressing whatever emotion the film is illiciting in you. If a movie is really good, it’s giong to make you laugh out loud, or scream with fright, or cry with sadness or happiness, or cheer and clap in excitment. A tv show or book or any other creative work that illicits emotion can rightly lead to an auible response regardless of whether the creators are there to appreciate it.
What jackdavinci said. I am an unashamed applauder at the end of a really good movie (most recent example being The Incredibles. WOOT! 
)
I got pretty good laughs when, at the end of LOTR: Return of the King, I said
“That was awesome! I can’t wait for the fourth one.”
And when I saw The Matrix right at the beginning of the subway faceoff between Neo and Smith, during the slow pan of the stare down, some guy in the theater let out with that stereotypical tumbleweed westernish sound:
“Boooweeoooweeeooonnngg. Waaa waaa waaaaaaa.”
Had the theater in stitches.
[HUGE hijack]
Wow! I always wondered about that place when I lived in East Austin. I’d pass it sometimes on my way home. It’s a lot like the rest of that part of town, a rundown graffiti-ridden ruin. 
I always like hearing old history about this town.
[/HUGE hijack]
Alright. Two good examples of things I said that went over well.
The first movie we watched last year was Superman IV: The Quest for Peace. There’s an awful scene wherein Supes and Clark Kent are supposed to be on the same double-date, and at one point, the man in blue burns the dinner to allow himself to escape. We watch him use his heat vision to overheat the turkey in the microwave, and because of the way the scene is edited, he appears to be intently staring at the bird.
For whatever reason I was inspired to yell “My turkey sense is tingling!”
But the quip I’m proudest of came a few hours later, during the horrible Roland Emmerich version of Godzilla. The heroes blow up Madison Square Garden, where 'zilla has laid hundreds of eggs. As they stare at the smoldering ruin - by which I mean MSG, not the Knicks - Godzilla, who had died half an hour earlier in the ocean, suddenly reappears from the wreckage. He nudges one of his dead lizard kids, then stands up to his full height and glares at the good guys. So I says…
“Chello! My name is Godzilla Montoya! You killed my babies! Prepare to die!”
We had, during a particularly big summer blockbuster, the THX sound at 11.
The screen says:
“The audience is listening”
And from the back, a young male voice:
“The audience is DEAF!”
At a screening of Big Trouble in Little China at my university, mumblety-mumble years ago:
Gracie Law (Kim Cattrall): “I can’t believe this is happening!”
Obnoxious audience member: “Me either!”
OK, it was me. But it got a laugh, so that’s OK, right?
Saw Charlie and the Chocolate Factory with a couple of other dopers. The theater was packed full, but really well behaved. The part where the miserable grandpa is ranting about how there’s no way Charlie will get the golden ticket is pretty sad, but it struck one audience member funny when he growled “YOU DON’T HAVE A CHANCE!” The man just had an outburst of laughter and that got everyone laughing for a minute. I don’t know why it struck him so funny, but it sure made everyone else giggle for a while. Now when I see that scene I always laugh to myself.
Reminds me of a recent one:
We were sitting in the middle row of Charlie, with a gaggle of kids nattering all around us, watching the movie. The part comes up where Charlie gets his first chocolate bar, for his birthday: he peels back the paper, everyone’s holding their breath, he tears off the tin foil, you could hear a pin drop…
…of course, there’s nothing underneath, just chocolate. No Golden Ticket.
In the silence, one guy in the back says, very loudly, “Awww, letdown!”
The entire audience dissolved. There was rolling in the aisles. It was brilliant.
Heh. I sometimes use the same line myself, though I’d go “The audience is now deaf.” Gotta have the “now”, y’know?
Stole it from Steven Spielberg’s Tiny Toon Adventures.