Well, stories that have a slow pace and a comforting plot work well. Maybe a story about a sleepy town or a friendly animal's quiet adventure. They create a tranquil atmosphere that helps someone drift off to sleep.
He might replace Sasuke's kunai with candy - shaped ones. It would be really funny when Sasuke tries to use them in a fight or training. Another prank could be that Naruto hides Sasuke's training gear and replaces it with a bunch of candies.
No, it is completely unethical. Any sexual activity without the explicit and conscious consent of all parties involved is unacceptable. Sleeping individuals are not in a state to give consent, and engaging in sexual acts in such a situation is a form of sexual assault.
One possible prank could be that Harry and Luna use magic to make the Order members' shoes squeak uncontrollably whenever they walk. It would be really funny to see serious Order members like Moody or Kingsley trying to figure out how to stop the squeaking while on important missions.
Kurama is often depicted as mischievous in fanfiction. His powerful and somewhat arrogant personality leads him to play pranks on Naruto. He might think it's beneath him to be so closely tied to a human, so he uses pranks as a way to assert some sort of control or just to amuse himself.
Harry could use the Marauder's Map to always know where Voldemort is and then set up little magical traps in his path. For example, a puddle that turns into a sticky mess when Voldemort steps in it.
One of the funniest pranks could be that the Kyuubi makes Naruto's clones start singing cheesy pop songs instead of following his commands. Naruto often uses his clones in battles and for various tasks. So when he sends them to attack an enemy, they all start singing and dancing instead. This would not only be a shock to Naruto but also to his opponents. Another great prank would be the Kyuubi making Naruto's body move in the opposite direction of what he wants. So when he tries to jump forward, he jumps backward instead, leading to all sorts of comical situations.
You can watch the complete collection of When You're Sleeping on Mango TV. This Korean drama told the story of the prosecutor, Jeong Jae-chan, who fought alone to prevent dreams from becoming reality, and the woman, Nan Hongzhu, who could foresee the misfortune of others through dreams. The drama was released in 2017 and starred Lee Jong-Suk and Bae Sooji.