It's a learned skill, figuring out an idea is a bad idea. As actual writers know, you have to generate so many of the buggers. Douglas Adams said, "An idea is only an idea. An actual script, on the other hand, is hundreds of ideas bashed around, screwed up, thrown into the bin, fished out of the bin an hour later and folded into thick wads and put under the leg of a table to stop it wobbling. And then the same again for the next line, and the next, and so on, until you have a whole page or the table finally keels over."
(Written before word processors, but you get the point.)
In thinking again about the story I'm trying to finish, dammit, I remembered what I once considered for its ending and thought Whoa, it's good I didn't actually write that. It was, in retrospect, terrible and possibly insulting to my friends who are New Yorkers. (It was a Matrix-y explanation for why 9/11 happened.)
OK, let's see if I can get out the other bad ideas, from both my works and others':
I drew a one-page comic strip in high school about a day in the life for a guy in the future. At the end, his home computer (somehow) panics as it warns him that police are about to arrest him. OK, computer panic is weird enough, but at first I wrote it not only panicking and warning him, but also saying "I love you I love you I love you..." Maybe it thought that was its last chance to say so? I came (partly) to my senses and erased those lines. The ending still didn't make much sense, though.
Earlier, in junior high when I knew less, I wrote a junior high-level bit of satire for the irregularly-published school paper about a bad day at school. An exaggerated, everything-goes-wrong day at school. Relatable, at least! (Though I think I wrote it in second person, with "you" this and "you" that. Arty.) But how to end it? I'm not sure why I ended with my main character relieved that a teacher told him not to worry about working in the class, as it was an art class. What teacher ever tells a student to slack off? And I'm sure I wasn't making a point like "art class is worthless," because I KNEW ART WAS AND IS IMPORTANT AND VITAL AND OFTEN REALLY FUN -- and I definitely got into art come high school -- but if I were making that point, I could've really sold the idea. Why would the character be relieved? Plus that's no real twist. The story petered out. I know, endings are hard.
Another junior-high-era story (by the way, like most of us, I didn't experience junior high so much as survive it) had a student fight a monster that burst out of the gym floor, Hellmouth-on-Buffy the Vampire Slayer-style...then get into trouble for being late to his next class. The end, followed by paraphrasing Will Smith's rap song: "So to you, all the kids all across the land, there's no need to argue, TEACHERS just don't understand!" OK, that at least reflects my fondness for how "Weird Al" Yankovic writes new lyrics to songs (more cleverly than that, but still), but WOULDN'T THE TEACHER HAVE HEARD THE GIANT EXPLOSION? Or at least have heard of it? Like, someone had run down the hall and yelled to everybody "Holy crap, there's a crater in the school gym floor"? Teachers notice stuff! Especially obvious stuff!
Teachers, I apologize for my unfair characterization of y'all.
Okay, I actually think this is a good idea, but I can't do anything about it as it's for a book I refuse to read ever again: Eoin Colfer's And Another Thing.... I was annoyed by the attempted follow-up to Douglas Adams's The Hitchhikers Guide to the Galaxy, and very early in the book, the one glimmer of hope I had that it'd be worthwhile petered out: Colfer describes an old man, and the description made me think Maybe that's main character Arthur Dent...but old and having gone back and forth in time and space so that, somehow, he's become the Man in the Shack who's so important in the second Hitchhikers novel! Think about it: Arthur Dent, ruler of the universe! Even if he is addled. That excited me. It seemed elegant. Then I read on and found that that was not so...and my interest deflated. (I was surprised recently to find that Colfer's book actually got some good reviews; when it was reissued in paperback, it had no blurbs, which I took to mean there were no positive reviews to quote.)
I loved the 1980s TV show Sledge Hammer! Certain the show would be cancelled after Season 1, the show runners ended the season with Sledge accidentally nuking Los Angeles. We then saw a cartoony painting of a wrecked L.A. (as Sledge's boss Capt. Trunk yelled "Hammerrrrrrr!") and the words "To Be Continued/ Next Season?" I was happy when the show got renewed; I was less impressed when the Season 2 premiere just said the second season took place five years before the events of Season 1. A cop out! Outrageous!
I would've been happy with a deus ex machina beginning. Because I'd seen the episode of The Young Ones where God shoots lightning to first shock a character then cook a chicken, I wanted God to turn out to be a Sledge Hammer! fan. God, shocked by the ending, would turn back time and find a way to keep the bomb from ever being a threat in the first place. Then the show would go on like nothing had happened! Extreme solution, but dammit, that's better than a cop out. Except maybe the producers decided it should be a copout, to make fun of copout endings of other shows. My idea? Too involved for that. But I can still picture it. Like I can picture this: