The CMC drink a potion that grows all of them into giants, turns Scootaloo and Sweetie Belle into hyper futas, gives Apple Bloom giant tits and makes all 3 of them super horny. Scootaloo and Sweetie Belle begin to fuck Apple Blooms nipples which makes them (and esspecially their stallionhoods and breasts) grow even huger and makes them even hornier.

“Sweetie Belle,” Apple Bloom groaned. “I feel weird.”

Sweetie Belle took a step back. “You feel weird? You look weird! You’ve got to be a foot taller!”

“What was in that potion?” Scootaloo choked out, doubling over. As Sweetie Belle watched, Scootaloo started to grow herself, inching up until she was of a height with Apple Bloom. Her clothes ripped off in tatters, buttons and seams popping until she was completely in the nude. Sweetie soon found herself looking up at the other two power Crusaders, each six-foot-six if she were an inch.

“You guys are huge!” she said, gaping - and then stumbled, her vision going black for a second. Luckily, Scootaloo caught her just in time- but by the time  Sweetie Belle came to, she was looking down at her friend. That wasn’t the only change. She became suddenly aware of a heavy weight between her legs that she could feel growing heavier by the second.

“Whoa,” Scootaloo said. She hesitated, then put a hand on the massive stallionhood that had grown between Sweetie’s legs. “Wow. I’ve never seen one of these up-close before!”

Sweetie moaned at the touch, shooting up a few more inches. She must have been nearly eight feet tall by now, the tip of her horn nearly touching the ceiling. Scootaloo nearly jumped as a spurt of precum shot out of the tip, nearly drenching her mane. “Oh, wow. That looks really sensitive!”

“Girls, what’s goin’ on?” Apple Bloom moaned off in the corner. Both  Sweetie Belle and Scootaloo turned to see her, Sweetie Belle’s massive member smacking against her chest as two equally enormous testicles began to swell against her thighs. “I feel so…crowded.”

“You look crowded!” Scootaloo said, eyes wide. Sweetie might have been over eight feet now, with Scootaloo just a half a foot behind, but Apple Bloom looked to be nearly twice that! She had her knees curled up to her chest and her head bowed low - though it still scraped against the ceiling. That wasn’t even the most surprising part, though. Sweetie found her gaze drawn to the two gigantic boobs hanging from Apple Bloom’s chest, her three-foot stallionhood hardening against her stomach as she realized that either one was even bigger than her head.

“We gotta get her out of here!” Sweetie Belle said, glancing around the treehouse wildly - and let out a yelp as her growing body hit the ceiling. “Ouch!”

She rubbed her head. “Scootaloo! What do you - “

But Scootaloo was paying her no heed. The other filly had sprouted a stallionhood of her own, and currently had both hands grasped firmly around her throbbing cock as she humped Apple Bloom’s growing tits.

Sweetie Belle squeezed her eyes shut as both she and Apple Bloom started to grow again. “We’re gonna break through!”

Scootaloo had her first orgasm as the trio broke through the roof of the Crusader treehouse, her monstrous cock convulsing as she grew from eight to ten to fifteen feet! Ropes of thick, sticky cum shot up into the warm air, coming back down to drench the other two with a chorus of splats.

“Mmff,” Sweetie Belle moaned, slowly coming to. She just barely registered an immense feeling of pleasure centered around her lower body. It was only when she opened her eyes that she realized that she was standing in the wreckage of their clubhouse - and that the vast majority of it was covered by a pair of massive, yellow-furred spheres.

Apple Bloom groaned as she shifted her weight, the ground shaking under her. She’d fallen over, belly-first, with each one of her enormous boobs lounging out in front of her. Standing up, she would’ve been thirty feet tall; lying down, each of her gigantic boobs was just about half that. Her two massive nipples protruded proudly from each one, and it was one of those nipples that Apple Bloom found had swallowed up a good half of her new stallionhood.

“Oh, wow,” she murmured. She was just able to see over the top of Bloom’s breasts, having reached a peak of twenty feet tall herself. Some part of her wanted to imagine how Rarity would react, how tiny her sister would be next to her. Another part of her wondered how she might “play” with her “little” sister. The rest of her mind was lost in the bliss of feeling her member penetrate Apple Bloom’s carriage-sized nipple, her precum already flowing freely enough to act as lube.

She gave an experimental thrust, loving the way her massive nuts slapped against Bloom’s bust, sending the whole mass of flesh jiggling and shaking like an earthquake. Beside her, she could already see Scootaloo going wild on AB’s left boob. Though Scoots might’ve been a whole five feet shorter than Sweetie, and just barely half Bloom’s size, she more than made up for it with a cock that towered above her head, easily reaching Apple Bloom’s nipple as she plunged in and out of it with gusto.

Panting, Sweetie Belle pumped her hips once. Then again, and again, and again, the need to fuck burning inside of her like a wildfire, all three of them moaning - and growing - all the while.