Aliens
Before lifting off to retrieve the remnants of the squad after the failed exploration. the pilot and co-pilot, check the cargo hold of the dropship, kill the alien intruder, pick up Ripley and crew, take off, and nuke the place from orbit, it being the only way to be sure, donchaknow?
(I can’t believe no one has mentioned this yet.)
No no no no no.
They get to the planet, listen to Ripley’s briefing, think again about what they’re potentially putting themselves in for, send in the android (hey, it’s not a real person after all) who confirms that the place is indeed one big xenomorph nest and they nuke the place from orbit, it being the only way to be sure (like, duh).
Fatalities/casualties/need for further unnecessary sequels: 0
Nah.
"…trees part and reveal King Kong, the giant ape, who looks with interest at her, then up at the natives, and roars.
He reaches for her, strips her naked, while she continues to scream, and, with huge brow furrowing, attempts to insert his gigantic ape-cock into her, transforming her in the process into a mushy mass of bloody chunks of meat. Frustrated, he stares at the mess now in his hand, shrugs as if to say, ‘Hell, I tried,’ tosses her over his shoulder, and gallumphs off back into the jungle."
Terminator—
The T-800 intercepts Sarah Connor in the Tech Noir bar, narrowly thwarted by Kyle Reese…quickly turning into a horrific melee when thirty four other time travelers from no less than thirteen alternate future timelines, including a eleven Terminators (including Skynet and Resistence-sent) of five different series’ (not counting models); three different iterations of Kyle Reese; two Reese brothers who were named Kyle but aren’t genetically identical to Kyle-prime; two partial cyborgs; eight different John Connors, ranging from ages 12 to 49, two of which are only half-siblings; three different Sarah Connors; Private Sumner, and two dogs, join in the fray. All were sent, alternately, to kill Sarah Connor and/or Reese-primes to destroy the Resistence(s) in the future; kill the T-800-prime to protect the Resistence(s) in the future; kill the T-800-prime to protect SKYNET(s) in the future; kill other prime time travelers before they could change history, or kill other time travelers before they could kill other time travelers who were going to kill the prime time travelers before they could change history. At least five of them were double-agents, renegades, or acting without orders do to malfunction or insanity.
Minutes later, the region of space-time around the entire bar finally ruptures under tachyon strain, and collapses into a rapidly evaporated singularity, leaving nothing behind but a partial vacuum and a hemispherical depression in the ground as smooth as polished glass.
The incident becomes a media sensation for several weeks; extraterrestrial or possibly Soviet involvement is speculated, but with little evidence left, nothing is ever proven.
Eventually, life goes on. President Reagan is reelected later that November. Michael Jackson turns 26.
(What? Time travel becomes a convoluted mess. That’s realistic. 
)
Not quite.
Sollazzo shoots Michael and Sonny wipes out every Tattaglia-esque looking person he can find, going mad and questioning the loyalty of everybody. When he orders Clemenza to kill Tessio for suggesting hiding the pistol in the toilet, Clemenza and Tessio instead kill Sonny, negotiate a peace with the Tattaglia, rebuild their strength, and then have a very bloody 1950 with the Tattaglia and Barsini families all but wiped out. Regime settles into Tessio as the new godfather (though it’s still called the Corleone Family) and Clemenza as his consiglieri, with Pentangeli (who’ll ultimately inherit) taking over Clemenza’s caporegime position. Tom Hagen survives the wars, moves to Hollywood, and becomes head of a huge lawfirm and talent agency that’s a front for Mickey Cohen.
Not quite.
Sollazzo shoots Michael and Sonny wipes out every Tattaglia-esque looking person he can find, going mad and questioning the loyalty of everybody. When he orders Clemenza to kill Tessio for suggesting hiding the pistol in the toilet, Clemenza and Tessio instead kill Sonny, negotiate a peace with the Tattaglia, rebuild their strength, and then have a very bloody 1950 with the Tattaglia and Barsini families all but wiped out. Regime settles into Tessio as the new godfather (though it’s still called the Corleone Family) and Clemenza as his consiglieri, with Pentangeli taking over Clemenza’s caporegime position and ultimately taking over the family when Tessio dies of natural causes and Clemenza goes to prison for the killing of Pauly.
Tom Hagen survives the wars, moves to Hollywood, and becomes head of a huge lawfirm and talent agency that’s a front for Mickey Cohen. Carlo gets whacked in the first gunfire, after which Connie marries Tessio’s gay son with whom she opens a successful day lily farm and later an orchid plantation and they live more or less happily ever after. Mama Corleone tries to kill Tessio but winds up being committed for a while then sent to an upscale retirement home in Boca close to where Fredo manages a whorehouse for an allied family; she’s filled with anger and bitterness until falling in love with a wealthy retired Jewish real estate mogul. Fredo dies at Mama Corleone’s second wedding from accidentally mixing vodka and battery acid. Kay remains in New Hampshire, marries an insurance salesman, has three kids, and only occasionally thinks of Michael, while across the ocean in Sicily Appolonia marries a local schoolteacher, has nine kids and is still alive to this day.
nice
The Wrath of Khan:
Terrell: Mr. Chekov, take us to the Ceti Alpha system.
Chekov: Ceti Alpha, now vhy does that sound familiar? Let me check something… Captain, there’s a standing Starfleet directive to stay the hell avay from the Ceti Alpha system. And now that I think about it, ve really don’t want to go there.
Terrell: Hmm, you’re right. Good thing someone thought to put that in the database.
Nah, McMurphy’s a drunken Irish brawler - not a type known for good impulse control & long term planning. He tried going along with the system briefly once he found out that they didn’t have to release him when his sentence was up, but he couldn’t do it.
Lord of the Rings
Gandalf in The Fellowship of the Ring:
‘Why thank you, Gwaihir the Windlord, swiftest of the Great Eagles, for rescuing me from the pinnacle of Orthanc and the evil clutches of Saruman. Don’t mean to be all “take take take” here, but could ya do me one more little favour? Fly that way and have a look out for two hobbits. You know, hobbits. Small folk, hairy feet, probably singing or eating mushrooms. Could ya hunker down and give them a ride east to Mount Doom? No no, you don’t have to wait long - they’ll only be a second. You will? Cheers!’
The End
Post-credit scene in Star Wars:
“Hey, Jabba, sorry about the delay. I have your money with a little something extra. Can I wire it to you? Okay, on it’s way!”
Say Anything
When Lloyd shows up in front of Diane’s house, blaring In Your Eyes by Peter Gabriel, she calls the police and has him arrested. The police issue a restraining order and Lloyd is not allowed within 500 yards of Diane. Lloyd is also fined for violating the noise ordinance that is still in effect in that community in the early hours of the morning. They both eventually move on and meet different people. The End.
Fan explanation : the Great Eagles don’t have the hobbit’s resistance to the One Ring’s corruption - so if Gandalf tries that, when they get to Mount Doom, the Eagle snags the Ring, drops Frodo into the lava, and flies off. Some years later, Middle Earth falls under the sway of the Black Lord of the Skies. 
You’ve Got Mail. Fox books moves in, and Meg Ryan’s store sees an increase in sales as more people come to the area to purchase books. By having a specialy store, Meg is able to draft off of the presence of a mega store. Soon she is able to build up a sizable nest egg, and marries a starving broadway actor who works in the shop part-time. [Books of Wonder in NYC, the model for the script, did just fine when the mega stores moved in]
The Breakfast Club. Students from different walks of life park themselves at a desk for detention and write a bunch of shitty essays, while staring into space for most of the time. They leave at the end of the day, never to say much more than “hi” to each other for the rest of the school year.
That’s different than the original? 
RAINMAN: Cruise’s character is arrested in California for kidnapping, extortion, and a variety of other crimes related to his abduction of his mentally impaired brother. He is sentenced to five years, released after 1.
I imagined a short story where someone builds the world’s first time machine. It’s finally ready for it’s first test; the inventor throws the switch… and the time machine is powdered into a pile of monatomic dust. On top of the pile is a sheet of paper which reads:
“Hopelessly irrepairable paradoxes threatened continued existance of human species. Only possible solution was to undo invention of time travel”.
This happens every time anyone ever tries to build a time machine ever again.
Partial cyborgs?
That’s not more realistic for that character, though. (And Randal doesn’t work at KwikStop.) It’s what a lot of other people would do, but Dante’s problem is that he wouldn’t.
Actually, I believe the explanation given by Tolkein is that the Eagles are not allowed to intervene in that manner by their master (whose name I’ve forgotten). I think there is even an explanation of this sort given in the book (though it may not have been expressed that explicitly).
In the lord of the rings commentary they mention that the reason they didn’t fly into Morodor, is that the nasgul would have flown up and killed them. Flying towards a giant eyeball tower above the treeline isn’t a good way to sneak up on it.