This sketch is the current cover art for Pinkie Pie Swallows a Cake. That story's short enough to fit in the description:

You held a mixing bowl in the kitchen of Sugarcube Corner, mixing batter without a care in the world, and then Pinkie Pie waddled her way in. Bulging from her sides was partially pregnancy, but mostly sweets she’d inhaled over the past few months. You’d at first expected her to be distressed at being unable to swallow anything and everything without consequence to her figure, but she never brought it up, and truly seemed unconcerned. She’d probably just lose all of that weight after giving birth to your child anyway.

It certainly didn’t impact her mood, and she hopped the rest of the way towards you. Unlike what had once been her usual bounce, she had to take breaks each time she landed, until she stopped swinging back-and-forth like a pendulum, but she slowly made her way across the kitchen to stand at the counter by your side.

“Hey hot stuff, whatcha cookin’?” She reared, however little, to rest her forehooves on the counter. You left the spoon in the bowl for a moment to pat her on the head, and she closed her eyes in appreciation. Then her nose sniffed and her head made its way towards the finished cake still cooling from its stay in the oven. You removed your hand and booped her on the muzzle, using your finger more than a little forcefully to keep her back. Only then did she open her eyes.

“That cake isn’t for you, at least not all of it.” Your voice was firm, and hers became sickeningly sweet.

“But I, Pinkie Pie, the mother of your cutesie-wutesie little foal, really want it for us.” She pouted, and teardrops formed in her eyes, causing you to look away. She’d been awfully fond of using “us” to mean “her” lately. You were about to deny “them” anyway when you turned your head back and saw her tongue already wrapped around the cake. The first time you’d seen her do that had scared the fuck out of you, but she only used her tongue like that in the bakery, and the bedroom. If you hadn’t already married and impregnated her, the sight would still scare you shitless.

Her tongue finished wrapping around the cake, and wormed its way underneath, somehow lifting it from the counter and walking it over to her gaping mouth. Saliva covered the counter, which you’d now need to clean. You winced as you watched her somehow fit the cake into her mouth all at once before swallowing, the three layer cake hardly making a dent in her throat as it went down. The entire gruesome act took maybe five seconds.

You put your hands on your hips and glared at her, but she wasn’t paying attention, eyes closed with a smile on her face and her tongue sticking out from the side of her mouth. That smile quickly became a frown, and she started to groan as she opened her eyes again. “Uhhhh.”

Well, you couldn’t stay mad at her until you knew she would be fine. You started to rub her back with your right hand. “Are you alright? Do you need me to get somepony?” You rested your left elbow on the counter to lean over and look at her face more closely. You thought about adding an “It serves you right.” but held off on that for now.

“Uhhhh. I-I need to sit down.” She hiccuped. She started to let her hindlegs give out from underneath her, and you held her butt to start leaning her to rest on her side, only for her to shake her head. She gently landed on her rump, with her back to the opposing counter, and began trying to lean against it, succeeding with your help. So, she wanted to sit like Lyra for some reason; it wasn’t the oddest thing she’d done, today. As soon as you finished leaning her back you could tell why.

You usually didn’t question how Pinkie Pie could swallow an entire cake only for it to disappear within her body instantly. Well, it seemed she couldn’t hide both a cake and a foal in her belly at the same time. You could see the cake in her stomach, or at least its detailed outline, poking out past her ribcage. You’d forgotten the lesson on pony anatomy Twilight Sparkle had given you, that unicorn excited to teach you in exchange for teaching her, but you got the feeling the anatomy lesson wouldn’t quite apply to Pinkie Pie regardless. Pinkie had her eyes closed, and she was still moaning. You comforted her with some headpats. Well, she seemed fine, and curiosity got the better of you.

You poked the cake, which still felt surprisingly solid as it gave away underneath your finger.

Pinkie swatted away your hoof, and her other hoof covered her mouth. Your eyes started scanning the room for a bucket but, thankfully, she belched loudly instead and started moaning again. “Uhhhh, don’t do that again.”

You kissed her on the head. “Just try to sleep it off, honey.” Immediately, Pinkie somehow goes to sleep sitting upright like that with her head tilted back, and starts to snore loudly.

After patting her on the head again and sighing, you stood and walked back to the other counter, continuing what you started. You took one look at the counter, still coated in saliva, and then set everything back down so you could clean up. You’d need to make another cake, too. You sighed again.

-

At least you were in the groove of things right now, so you really had little trouble resuming your baking. Soon enough, the kitchen was full of delicious smells once again, and a fresh cake was cooling on the counter before you iced it. You made sure to steal glances at Pinkie Pie occasionally, still snoring; every time you looked, the cake-shaped lump in her belly was less cake-shaped. By the last time you checked, her overall belly was a little bigger, poking out just a little bit more, without any painful lump jutting out from the top of it.

-

Another cake was finished, placing you right where you’d been when Pinkie had first come to see you. Her snoring was broken by a yawn, and you turned to see her flutter her cute little eyes open. “Wowie, I sure feel better!” She rocked herself forward and managed to stand by herself. Then she waddled her way over to stand at the counter by your side. She reared, however little, to rest her forehooves on the counter after noticing the new cake. “You know, all that sleeping has made me hungry.” Both of you laughed, but it seemed she waited for your eyes to close before snaking her tongue out towards the cake for a second time, which you gently pressed to the counter with a finger.

“Uhhh,” it was hard for Pinkie to speak with her elongated tongue pinned like this, but she managed, “I whas jus’ playng ’round?” She tried to smile at you.