A term I just came up with.
I think this may be part of why I dislike reading sword and sorcery / fantasy screenplays… for some reason, with those babies, logic is often gaily tossed to the four winds. At least that’s the case when my students write in that genre. And my clients. And some movies that get made.
Seems that if you’re writing a searing personal drama about a woman whose husband dies and she has to get the cotton crop in… all logic is there and workable. She doesn’t plant the cotton and then have horrible boll weevils and suddenly (right at the opportune moment!) remember her Grandmother’s wonderful boll weevil elixir hidden in the back of the icebox… that asinine method of solving problems is rare in dramas.
But not in fantasy.
Just because it’s fantasy, doesn’t mean it isn’t real. You’re creating a real world with real rules, and you (and the characters) must follow them. All the time.
So no “As Needed Gifts.”
Do not give your character a boon just because he needs one right then in order for the plot to move forward. Do not give him a special skill that has never been mentioned up to now, just because he needs it right now! If he needs to levitate on page 45, show him playing with his little sister, levitating in the back yard, on page 5.
Do not suddenly have him know how to repair WWII clocks, right when he finds a clock that doesn’t work. Have it be his only hobby from page one. Do not suddenly have him know how to play sitar, right when he is about to be murdered by sitar carrying thugs.
If he has a gift, a skill, a tool, a talent… make sure we know about it early, then forget about it until that gift is needed. In real life, in drama, and in (I swear!) fantasy stories, nothing can be there the instant you need it, unless it was there all along.
Check your script and get rid of all As Needed Gifts! Let me know if you find some…
Your Screenplay Sucks! 
What about the situation where you want to slowly reveal an ability, like in the Matrix.
For example, there’s a scene where the protagonist is being trained in combat, and the master keeps putting his pupil to the ground.
The first time you see this, it’s filmed in such a way, that you’re led to believe, for example, that the problem is with the student. But later, when the master is attacked by ninjas, it’s revealed that he’s actually a real badass, and what he’s actually doing is moving superhumanly fast.
And, of course, later the student finally learns how to do the same thing (part of the tension is will he learn?), and defeat the bad guy.
That sounds like just the right way to do it. What I’m talking about (in its lamest extreme) is a guy chased into a men’s room by thugs and they’re beating him up and he’s about to go down for the last time, when he dives into the stall, reaches up to the old fashioned toilet tank and finds a loaded .45 automatic and shoots them all. A gift the author gave him, right as he needed it. I see it a lot. Your situation ain’t that…
the ol’ Deus Ex Machina.
Yeah, my fave…
In contrast to fantasy, what I regard as the better end of science fiction tries to introduce one impossible thing, right at the beginning, and work through the ramifications of that. This has the nice side effect of largely making it impossible to fall into the trap you have correctly identified.
Jorge Luis Borges commended this approach, saying that H.G. Wells wrote one book about aliens invading Earth and another about an invisible man; to have written a book about invisible aliens invading Earth would have been artless.
(I realise that this is the second time I’ve posted a comment on your blog using H.G. Wells as an example. I’m not sure why that is!)
While it was a little discouraging to hear that you’re not a fan of reading Sword & Sorcery/Fantasy scripts (is it the genre or the writers that turned you off?), I was very pleased to have come away from the article knowing that my fantasy screenplay has not one ‘as you need it gift’.
In fact, in the sixth months I spent plotting and outlining the story before even beginning the screenplay, my paramount concern was that it was logical, accountable and obeyed the rules I had set. Mainly, because, like you William, I grew tired of fantasy writers using the genre as a crutch and thinking they can introduce anything to aid their protagonist without foreshadowing, simply because it wasn’t set in the real world.
I’ll zip you my script for assessment when I’m happy enough with it to do so (in my 4th draft) as I want it to be as strong as possible (obviously). Who knows, if it’s good enough, it may get you back to liking the genre! 😉
P.s: I made sure I proofread this post!
I’m thrilled about this post, another name for the “As Needed Gift,” someone mentioned it above, is “Deus Ex Machina,” and while the ancient Greeks may have used it in stories like Medea to create a lavish twist ending, in the modern world it is a hallmark of straight-up BAD WRITING. I really can’t believe even students would actually use this in work that they hand-in for a grade. I wouldn’t let them pass the class without fixing it.
Also, I might get some hate for saying this, but: this is why The Lord of the Rings movies are better than The Lord of the Rings books. Tolkien brought characters in and out of the story to either save the heroes or thwart the villians as they were needed (Glorfindel, a character absent from the movies, is a classic example). While Jackson either expanded the roles of characters who were already essential or cut out tangential plot-lines altogether if they went too far off course, the films had a greater flow of continuity and a tighter, more engaging story because of it.