Zipporwhill pulled out a toy that she just loved to use, a light blue strap-on. She put it on around her waist, then surprised Fluttershy by getting on her knees, burying her face in between her ass cheeks and instantly sucking on her asshole. This was incredible timing because as Fluttershy got the shock of her asshole suddenly being tended to, Ripley let out a small howl and blew his hot doggy load into Fluttershy's mouth, his spunk flooding her tongue as it pooled in her cheeks. Fluttershy had no choice but to swallow all of his warm sticky cum and allow his knot to deflate before letting his cock slip out of her mouth, then with a smirk she looked back at Zipporwhill and said "I see the birthday girl wants to get involved, huh?"

Zipporwhill nodded before pulling away and giving Fluttershy a smack on the ass, then she lied back on her bed and said "Get your fucking ass over here, Ripley is still hard so he can have your pussy while you bounce on this cock. Seriously, if it wasn't so awesome having a pussy I'd swap it out for a massive dick and set of balls in a heartbeat".

Fluttershy giggled and climbed onto the bed, then facing away from Zipporwhill, she angled herself so that Ripley could fuck her in the missionary position even while she was having her ass pounded. Fluttershy lowered herself down and with Zipporwhill's help slid the entirety of the strap-on up her ass, she patted her wet pussy and said "Come on Ripley! Here boy!"

Ripley who had become slightly soft went back to full hardness again at the thought of entombing his dick in Fluttershy's needy pussy. He hopped up onto the bed and wrapped his legs around the curve of Fluttershy's hips, then after some careful guidance his cock managed to push its way past her folds and into her hot moist vagina, Zipporwhill similarly grasped onto Fluttershy's torso with both hands, they were all ready to fuck.

As soon as Ripley starting pumping away at Fluttershy's pussy, Zipporwhill immediately started pushing her hips upwards to fuck Fluttershy's ass, using the momentum of the springs in her bed to bounce her hips back up on every downwards movement, making the bed squeak. Fluttershy went cross eyed and her tongue hung out of her mouth, bordering on full aheago face, she had never been double teamed before, the experience of having her ass and pussy fucked, not to mention one cock was canine while the other was human, her body responded by simply flooding Fluttershy's brain with dopamine and triggering a cascade of orgasms throughout the session.

Fluttershy felt herself almost going insane with pleasure, how had the thought of being fucked by more than one cock in multiple holes never occurred to her before? It was fucking awesome! She groaning loudly with occasional interval of what Zipporwhill assumed was Fluttershy attempt at words of some kind, Zipporwhill reached her hands further up and groped Fluttershy's tits, squeezing them, pulling and twisting her nipples. The intensity of Fluttershy's repeating orgasms increased, she didn't know how much more she could handle, Ripley was still going and his knot had barely started to grow, Zipporwhill was only getting harder and faster with her fucking if anything, Fluttershy wasn't sure how much more her body could cope with before she lost consciousness from over-stimulation and passed out, she desperately didn't want to faint whilst getting the best fucking she had ever had in her life!

Fluttershy somehow grasped onto the faculties in her mind required to keeping her awake, clinging on to her sanity as every depraved sexual fantasy played out both physically and mentally, her brain was alight with reactions beyond comprehension. It all came to head as Ripley howled and rammed his knot into Fluttershy's pussy, a pumping a second much larger load into her tight, clamping and absolutely drenched fuck hole, whilst Zipporwhill used all of her muscle power to give one powerful thrust upwards, the strap-on reaching the deepest point in Fluttershy's ass it could reach. Before Fluttershy finally gave up and allowed to sleep to claim her, simply collapsing with Ripley stuck in her pussy and Zipporwhill, slightly crushed and unable to move under the weight of Fluttershy's body.

After the birthday party was over, everybody left, nobody had noticed that Fluttershy and Zipporwhill had seemingly disappeared for a quick and unexpected fuck that involved her dog. Before Fluttershy left Zipporwhill said "Hey, I'm currently in a committed relationship with Scootaloo, so don't expect what happened up there to become a regular thing. However, if at any time in the future you wanna come round here and fuck my dog? Just do it" she smirked.

The End

Author's Note

Thank you Undead Man for this story idea! I hope you enjoyed it! :)