Maud has sex with Everypony.

Maud stepped off of the train into the dusty Ponyville air with a soft sigh. She wasn't entirely certain why it was she had decided to re-visit her sister, and if she had to force herself to come up with a reason, it'd be because she just cared enough about her to stop by. She had hardly got a chance to glance at a rather intriguing-looking hung of igneous rock just off to the left of the platform when a pink-colored streak of energy tackled her. Or at least, they tried to. Maud was rather used to Pinkie's exuberant displays of affection, and as such barely flinched when her sister blasted full-bore into her flank. Pinkie seemed unfazed as she began to laugh and rub her cheek all over Maud's neck.

"I'm SO glad you could make it again, Maud! You're in for a real treat!"

"I love surprises." Maud drawled, a hint of a smile curling the corners of her mouth up as she stoically disengaged from Pinkie. Pinkie just bounced around her in a circle, doing three laps for every five feet Maud walked.

"That's awesome! Because I TOTALLY forgot what's going on this week!" Pinkie giggled as she came to a halt, her hair bouncing with inertia as she beamed at Maud.

"What did you forget?" Maud mumbled, glancing longingly back at the igneous boulder.

"This is Heat Week!" Pinkie squealed, her flanks quivering with what Maud would guess was excitement. That, more than probably anything else in the history of... Well, ever, made Maud react. She blinked at Pinkie twice and opened her mouth a few times. When she was finally able to sort her thoughts, she managed a few words.

"What's 'Heat Week?'"

"Well do you remember when you, me, mom, dad, and the sisters lived on the rock farm? How when we started to grow up a little bit more, we all started to get this period where we'd all get kind of irritable and snippy with dad, so much that he just left for the whole week?"

"Eer... Yeah, kinda." Maud didn't exactly like where Pinkie was headed with this...

"Well, Ponyville's got so many mares in it, we ALL do that! But the stallions here don't mind us getting all snippy and whatnot! They just roll with it. In fact, some of them enjoy it! Look!" Pinkie gestured with a sweeping hoof out to the town center, beaming as Maud laid eyes on something she'd never expected to see before.

Everypony she saw was either fucking, or about to be fucking. Mares went down on mares, stallions teamed up on mares, and some mares just unabashedly masturbated in front of everypony.

"Eer... Pinkie, I don't think I should be in Ponyville this week..."

"But you're still on the same cycle as me, right?!" Pinkie beamed, bouncing around her in a circle again. Maud became painfully aware of the smell that seemed to permeate the air just then. The musky, heady scent of arousal and sex wafted past her nose, reminding her of how long it had been since her own last sexual encounter. At least, one that didn't involve an amazing deposit of malachite or some completely fascinating sedimentary boulders. She squirmed her thighs together, glancing about before coming back to Pinkie once more.

"I'm on my cycle, yeah, but..."

"But nothing, silly!" Pinkie Pie flipped over Maud, using her flanks as a vaulting board to land behind her. Maud looked over her shoulder as Pinkie unceremoniously lifted the hem of her dress. "Just relax and join the fun! I promise you're going to enjoy it more than your last visit!"

"Pinkie..." Maud blushed as her sister lifted her tail, exposing her backside. "That's- hey." She stopped short as Pinkie wasted no time diving in, her tongue sloppily dragging over the epicenter of her heat. Maud felt pleasure rock through her core, not unlike molten magma. Ooh... Magma... The thought sent a shudder along her flanks, making Maud close her eyes with a soft sigh. Pinkie's tongue lashed at her core, eliciting a waterfall of saliva and juice. Maud pulled at the neckline of her dress, feeling hotter than she had in the confines of the rocking train.

"Hmm! You taste yummy!" Pinkie bubbled, her quick sentence sending a hot wave of her breath washing over Maud's stomach. She lifted her rear leg a little bit, flexing her muscles as Pinkie continued to lick.

"P-pinkie..." Maud shuddered, placing her hooves back on the ground once more. She grit her teeth and tried to resist it, but the long time it had been since her last partner and the scent of sex in the air coupled with her own heat cycle brought Maud to orgasm quicker than she could react. Pinkie pulled away from Maud's dripping cunt with a giggle, her eyes closed as Maud squirted a thin stream of liquid onto her face.

"Wow! That was super quick!" Pinkie cartwheeled around to Maud's front, plastering their lips together for a musky-tasting, rough kiss. Maud just blinked and blushed a little.

"It's been a while."

"I can tell! But you came to the right place at the right time!" Pinkie spun around, eyeing the relatively large group of ponies in the town center. "Let's see if we can't find somepony to help you out... Ahah!" Pinkie grinned as she shot off faster than a rocket, fishing a stallion from among the many ponies going at it. Maud watched with mild interest as Pinkie dragged him over towards her position.