Twilight was on her fourth day of a study session. She had found a scientific subject that fascinated her (which none of her friends understood), and had read several books on the subject, which she had finished yesterday, and was now reading more about it online, thinking she could invent something related to it.
For four days, she only ever paused this to eat, sleep, go to the bathroom, feed and walk Spike, or hang out with her friends - but not shower.
It was a hot summer day, so she wore her Legend of Everfree outfit, which she had not changed out of since starting her study session. She even slept in it, as she'd stay up pretty late and only go to bed once she was really tired.
Spike walked into the room. "Hey Twilight. It's almost time for the party at Pinkie's house!" He sniffed. "Phew! Twilight, you really need to take a shower."
Twilight sniffed her armpit and recoiled slightly. "I'll finish my study session after the party. Then I'll shower."
"And maybe change out of that stinky outfit."
Twilight finished reading the web page she was on, then she got up and walked out the door with Spike. Spike made sure to walk upwind of her.
...
When Twilight arrived at the party, all her friends were already there. They walked up to welcome her to the party, but as they got close to her, they sniffed and look disgusted.
"Good heavens, what is that smell?" said Rarity.
"It wasn't me," said Rainbow Dash.
"That would be Twilight," said Spike. "She hasn't washed since she started her study session four days ago."
"Oh, you poor thing," said Rarity. "I know how to fix that. Pinkie, get a bath ready."
"On it!" Pinkie ran into her bathroom and turned on the hot water, pouring soap into it.
"I don't need a bath, really," said Twilight.
Rarity sniffed Twilight and wrinkled her nose. "Yes, you do," she assured her.
"I was going to shower tonight."
"You simply cannot go through the party smelling like that."
"You put up with Rainbow Dash and Pinkie Pie farting."
"Yes, well, I still prefer if they didn't, and besides, that smell goes away after about a minute. Your smell won't. Besides, Fluttershy and Applejack each gave me a bath once, and it was very pleasant."
"Bath's ready!" said Pinkie.
"I'm not taking a bath today," said Twilight.
"It'll be fun," said Sunset. "Remember when you gave me a bath?"
"I'm more of a shower girl."
"Well, it's too late to change it now," said Rarity, and she and Sunset reached for Twilight.
Twilight tried to run, but they caught her and dragged her to the bathroom. She resisted, but it wasn't nearly enough to slow them down. They got her in the bathroom and threw her into the tub.
"Once we're through, you'll smell lovely," said Rarity, removing Twilight's glasses and putting them on the counter.
Twilight tried to stand up, but Sunset forced her back into sitting position while Rarity filled a bucket with warm water and poured it over Twilight's head, soaking her hair and T-shirt.
"Okay, I'm clean and wet, can I get out now?"
Rarity sniffed her. "Not yet. Sunset, hold her while I wash her."
Twilight squirmed a bit as Sunset held her in place. "Sorry about this, Twilight, but she's right, you smell awful."
Rarity poured some shampoo on Twilight's hair and started to lather it. "Your hair really needs this, Twilight."
Once Twilight's hair was saturated with shampoo, Rarity put some soap on a bath scrubber and scrubbed Twilight's sides, armpit, and back, creating suds all over her shirt. Twilight continued to try to resist, until she accidentally farted in the tub. She blushed and sat still. Rarity groaned slightly in disgust, but said nothing and continued to scrub, while Sunset chuckled a bit.
Eventually, Rarity finished scrubbing Twilight, and her armpits smelled only of soap. "Now, to wash her rear end."
"Can I do that part?" said Sunset.
"Of course," said Rarity. She got Twilight in a position so she was on all fours, and Sunset poured a large amount of liquid soap onto Twilight's butt and started to scrub it, covering her stinky shorts with suds. Twilight blushed, but a part of her enjoyed having her behind washed by Sunset, after doing the same to her.
Once Sunset was done scrubbing Twilight's butt and upper legs, she got Twilight back into a sitting position and lifted her feet onto the sides, removing her shoes and pouring the water out into the tub. Rarity removed Twilight's smelly socks, cringing as she threw them into the tub, and scrubbed her feet, making sure to get every inch of them clean, for they smelled as bad as her butt and armpits.
Finally, Rarity finished, and Sunset set Twilight's feet back in the tub. Rarity poured another bucket of water over Twilight to rinse the soap and shampoo off, then drained the tub. Sunset poured one more bucket over Twilight once the tub was empty, save for her.
"How do you feel?" said Rarity.
"Clean," said Twilight, who no longer smelled bad. "I suppose I did get a little carried away..."
"If you can find time in your study sessions for us, surely you can take a few minutes out of them to shower."
"You're right, I'll do that in the future. Sorry about the smell."
"It was kind of fun giving you a bath."
"Yes, it was," said Sunset, winking at her. Twilight giggled.
"And now the party can begin!" said Pinkie Pie.
Despite being soaking wet, Twilight enjoyed the party, as did everyone else.