Celestia and Luna headed up to Canterlot's wealthiest area. Wealthiest besides their own anyway. They couldn't stop snickering to each other about what kind of pranks they'd pull. There were the classic options, like "ding-dong-ditch" (or "ring and run", as Luna preferred to call it), but they could also come up with some naughtier ideas. The only rule was, of course, don't hurt anypony. The goal was to have fun, not be malicious.
It only took a short time after they arrived to spot two nobles they wanted to be their first targets: Prized Eyes and Special Hue. Luna knew them from her most recent session of nightly court, where they'd instigated arguments among some of the other representatives to try to gain Luna's favor.
"It was their first time in my court," Luna explained to Celestia. "They swore they wouldn't rejoin my court with the most false politeness I've seen."
"Seems they thought they could win your favor if they couldn't win mine," Celestia replied. "It's been months since they've been in my court. I've started to realize our courts share much of the same nobility. Seems they've somehow gotten the idea if one of us won't agree, the other will."
"You speak as if they're subtle about that, Sister," Luna remarked.
The sisters crept to hear what Prized Eyes and Special Hue were discussing, but kept certain to remain hidden from view. Unsurprisingly, they were complaining about the day and night courts being cancelled, and Luna's refusal to grant their requests at her previous courts. Prized Eyes, in particular, was also hinting at joining Luna's next session of court. So much for not rejoining.
Luna looked around and got an idea when she spotted some thorny bushes. With her magic, she inconspicuously grew out one of its thorny branches and laid it in the path of Prized Eyes and Special Hue. Distracted by their conversation, neither pony saw the branch in their way until they fell for it. Prized Eyes stepped right onto the branch's small thorns while Special Hue tripped over it, though not enough to give her a hard fall onto the ground.
"We must demand the princesses order these awful plants to be cut!" Prized Eyes snapped as he helped his wife up.
"Agreed," Special Hue remarked snobbishly. "How any respectable pony would allow such trifling plants on their lawn is beyond me."
They walked away, continuing their conversation of complaints, as the royal sisters let their laughter burst out of them. Celestia praised her sister on such a well-executed prank. Luna used her magic again to shrink the branch back into its bush. Now, it was Celestia's turn. They walked on, searching for the next noble to be their prank victim. The search took little time.
Celestia's chosen next target went by the name of Ornate Opal. For her, the prank to pull was so obvious, she felt uncreative in selecting it, but she went on with it anyway. She picked up a decently sized rock and disguised it as a jewel, enlarging it a slight amount. She levitated it over to Ornate Opal's face. The moment he saw it, he wanted it and tried to grab it, but Celestia yanked it out of his reach. He tried to grabbed it again, but Celestia moved it out of his reach a second time. This time, Ornate slowly crept up on the gem before making a grab for it, but again, his attempt was useless.
Luna's face was getting sore from struggling to hold in so much laughter as she watched her sister toy with this pony like he was a cat. Finally, after twenty-two attempts that Luna counted, Celestia cut the poor noble some slack and undisguised the gem to reveal it was a rock. Ornate was furious, but Celestia and Luna hurried out of sight before they could be spotted. Ornate smacked the rock away before resuming his noble posture and continuing on his way, though he silently swore beneath his breath he'd make a formal complaint to the princesses about the mysterious prankster.
"Sister," Luna said, her words juggling with her laughter, "if it wouldn't cause us so much grief, I'd propose a contest of who can garner the most complaints for our next court sessions!"
"Oh, no, Luna!" Celestia laughed. "I could never do that to you! Granted, we won't have the grounds to complain tomorrow. We deserve the complaints."
"It may sound irrational, sister, but I'd prefer earned complaints over petty ones," Luna admitted. "I worry more about how to contain our laughter!"
The night of pranks went on, each sister taking turns choosing an unsuspecting member of nobility and a prank to pull. They did some of the classics and some non-classics, but not one prank went off without laughter that was only stifled to avoid being caught. As their fun went on, they remained in agreement whatever grief they got from their courts the next day and night would be worth it. They truly couldn't recall a time they'd had so much fun together.
Of course, all fun things had to come to an end and the sisters eventually realized they had to bring their prank night to a close. They were tired, but it was pleasing way of feeling tired. Luna was already beginning to fall asleep, no doubt because the spell that allowed her to maintain energy from the dreamscape was wearing off. They began on their way toward their castle, Celestia flying with Luna on her back just to avoid any suspicion from seeing a unicorn flying in the night.