Rainbow Dash was annoyed because Pinkie Pie took about 20 mugs of cider, and she didn't get any. This time she had told every pony in Ponyville except Rainbow Dash and Fluttershy about her plan to camp out, ensuring that neither of them get any cider. The other times she was just being Pinkie Pie, but this time was deliberate. After the Flim Flam brothers came in and became the Apples' competitors, Rainbow Dash tried to think of a plan to get revenge on Pinkie Pie. Finally, an evil idea came to mind. Pinkie had drank a LOT of cider, and she was going to use that against her!

...

When Pinkie Pie got home, she found a note saying there was an exercise competition, and that the winner would receive a big cake. Pinkie was so excited for this she immediately put on her exercise outfit - a yellow tank top and skintight teal shorts - and ran to the location mentioned on the note. She saw no one was there, so she figured she must be early. She began doing some sit-ups, while Rainbow Dash waited patiently with a thundercloud.

After a while, Pinkie had to pee. She had drank a lot of cider. She hadn't had to go this badly since that time she was on a train to Dodge Junction. It was a horrible train with no bathroom, but at least she made it that time.

There was a bathroom in this area, with a thundercloud a few meters above it. Pinkie ran toward the bathroom as fast as she could. Anticipating Pinkie's speed, Rainbow Dash lowered the cloud closer to Pinkie, and just as Pinkie was putting her hoof on the bathroom door, Rainbow kicked the cloud. Lightning struck next to Pinkie. She jumped and peed herself, much to her dismay.

She peed for about 30 seconds. She stood there as she felt her shorts grow damper and damper, and waterfalls of pee flowed down her legs and onto the grass below her. Though she did feel a sense of relief, she hoped no one was here to see this.

"Gotchya!" said Rainbow Dash. "That's what you get for keeping me from getting any cider!"

"I'm sorry Rainbow Dash," said Pinkie. "I won't do it again. Cross my heart and hope to fly stick a cupcake in my eye."

Rainbow could hear the shame in the pink mare's voice and knew she meant it. She now felt bad about forcing her to wet herself. So she jumped on the raincloud so it rained on Pinkie Pie, completely soaking her in a matter of seconds. "You can just say I made it rain on you in the middle of an exercise as my revenge."

Pinkie gave Rainbow a hug, and bounced away cheerfully as though nothing had happened. Now that she was spared total humiliation, she did think it was kind of funny...

Author's Notes:

Yeah, I get a little soft near the end because I don't want the ponies to suffer too much, even after what Pinkie did here. Also, I give them outfits because that's just how I like it.

After I revoked my submission the first time, I added in that last part at the end as another user's suggestion on the My Little Fetish forum, in case I changed my mind, which I did if you're reading this.

I also added a little more detail to this chapter in response to complaints about the quality.