Unmentored and in Charge
This technique follows up on Goten and Trunks's story that I talked about last post on Stacked Tripling. So, at this point in the series, Trunks and Goten are the world's only hope. They're done crying, and they're ready to train and prepare to fight the super villain Buu. Their mentor, Piccolo, shoves them into the Hyperbolic Time Chamber (a room that slows down time; one day in our world equals one year in the time chamber), so the kids can quickly get more training in, while he holds off Buu.
Goten and Trunks have no mentor. The only person still alive that can teach them fighting techniques is trying to hold off Buu. So, they have to train themselves.
So what do a naive seven-year-old and eight-year-old come up with? The stupidest, most childish fighting techniques in the entire series! The kind that make you want to facepalm. Moves they've named things like "Galactic Donut," and "Screaming Angry Wombat." They've watched too many cartoons, and they're trying to copy them.
This creates an interesting dynamic in the story. By this point in the saga, we've seen that Piccolo doesn't have full control over Goten and Trunks (or rather, Gotenks). They have a mind of their own. They're the most powerful people on the planet. But they're some of the most childish and naive.
Many stories have characters that have mentors to help them grow and develop. In most stories, the character trains under the mentor for months or years and then the mentor dies tragically. We've seen it a hundred times. Why not switch it up? Like DBZ did? What would your character do, what would he come up with, if his mentor was out of the picture earlier? (Temporarily or permanently?) And since the world depends on your character, she'd have to come up with something!
Or, what if you made the character very unfit to be the hero in some way? Goten and Trunks are unfit because of their age, naivety, and innocence, but, that's all we have to work with! Too many times, the hero is too fit for his role. Give him a quality that is a major set back for someone in his position to have.
You can't have Your Cake and Eat it Too
Hopefully we've all heard the saying "You can't have your cake and eat it too," meaning, you can't have two things at once. You have to pick one or the other. You either eat or your cake, or you have your cake.
What happens if your character tries to pick both?
In the Buu saga, Buu throws a blast that has the power to blow up the Earth. Goku and Vegeta are fighting him at the time, and they aren't strong enough to block the attack. Their only option is to use instant transmission (teleportation) to leave the planet to save themselves.
But their sons, Gohan, Goten, Trunks, and their friend, Piccolo, are all unconscious on the ground, so they have to grab them first, before Buu's blast hits the Earth. As Goku heads for them, he sees two other innocent people (Dende and Hercule) nearby, and being the hero he is, he can't leave them to die either. He wants to save everyone. Dende and Hercule are closest, so he grabs them, but then he doesn't have time to get the others! Vegeta and Goku teleport off the planet as their own sons are blown up.
In Goku's rush to save everyone (a very noble trait), his own children died! Not only is that awful in and of itself, but now Vegeta is mad at Goku, and imagine how awful Goku himself must feel. That's terrible!
So in this plotting tool, the character wants to have the cake and eat it also, but in the process, he loses what's most important to him. If you use this tool, explore how the character feels about what happened, how others feel about the situation, and, how the situation alters the plot.