Based on the following pics: 
https://derpibooru.org/1049930
https://derpibooru.org/1067071

>Be Anon stopping by Sugarcube Corner for some late breakfast.
>Pinkie Pie sashays over to your table with your food and coffee.
>She leans over as she sets your platter on the table giving you a fantastic view of her cleavage.
>Dayum that girl has some superior sweater puppies!
>Seriously, getting to ogle Pinkie's thick curves is one of the best reasons to come to Sugar Cube corner.
>Besides the coffee, that is.
>You think about chatting her up a bit when, all of a sudden, she stands up strait and perks her head like she's listening for some faint noise.
>Without warning the fingers on her left hand start wiggling, then she shudders.
>"Noteworthy..." she mutters.
>Then her left eyes twitches rapidly and her right shoulder jerks.
>"Broke..."
>The young woman's knees knock together and she sneezes violently.
>"A Pinkie Promise!" she gasps in shock as she finishes her bizarre routine.
>"Noteworthy broke a Pinkie Promise..." Pinkie Pie repeats, her voice taking on strange edge.
>You start to ask if everything is ok but pause when you notice the manic look in her eyes.
>Her breathing speeds up and gets heavier - it looks like she's working herself into a frenzy - and all the while she keeps repeating, "Broke a Pinkie Promise... broke a Pinkie Promise..."
>Then you notice something strange.
>Your server's clothes are beginning to look rather tight on her.
>As you look on, Pinkie's top gets tighter and tighter, with stress lines starting to appear across the fabric.
>You sit entranced as diamond shaped gaps form inbetween the buttons along the front of her shirt, displaying an increasing amount of cleavage.
>Managing to tear your eyes away from her busty display you are shocked to see that Pinkie looks taller than she was a few moments before.
>By this point it's not just her bustline that's straining.
>The shoulders of her blouse look like they're ready to come apart at the seams and her skirt is pinching her waist something fierce.
>The growing girl keeps sucking in great lungfulls of air and exhaling them with her angry chant about broken Pinkie Promises.
>You realize that with every breath she takes her form puffs up a little more.
>In matter of moments Pinkie's shirt bursts it's buttons and her glorious gazongas come spilling out.
>Her huge bra has already failed and fallen down around her midsection. 
>But she's not naked - her jiggling melons are instead restrained by a skimpy black bikini - one that in no way is a match for her heavy, heaving hooters.
>In fact, the swimsuit's tiny cloth triangles barely seem to cover her most essential bits and you can clearly make out her inch-long nipples puckering the dark cloth.
>A few more deep breaths and the gigantic girl's shirt starts to come apart at the shoulders.
>Another few huffs and puffs and the waist band on her dress snaps causing it to fall down around her ankles.
>Her lower half is now clad solely in a bikini bottom that matches her inadequate top.
>A bottom that is rapidly being swallowed by her thickening thighs and swelling booty.
>The puffed-up party planner leans back and takes one final breath, deeper than any she's taken thus far.
>Her chest swells and expands until finally...
>SCHRIIIP!
>Her shirt completely explodes off of her titanic torso!
>You can only gawk as you stare at the female before you.
>She stands a good two feet taller than you, clad only in a tiny string bikini, and sporting what seems like miles of tits and ass.
>Not only that, but as she finishes removing the last shreds of her ruined clothing you can tell that under her plump flesh this massive mountain of a woman has some serious muscle going on.
>Without even a glance in your direction, the sudden amazon charges towards the front door of the shop.
>It looks as though she's going to crash through it like a bulldozer.
>Instead, the juggy juggernaut stops suddenly, reaches for the door with sausage-sized fingers, and gingerly opens it.
>Once she squeezes herself through, Pinkie raises her arms and roars, "YOU BROKE A PINKIE PROMISE!!!" and takes off down the street.
>As the busty behemoth thunders out of sight you don't even notice that Mrs. Cake has come up beside you until she starts speaking.
>"Oh dear," she says, leaning over and picking up her employee's tattered clothing, "It looks like someone broke a Pinkie Promise. But at least her emergency swimsuit held this time."
>The proprietoress gives you a sympathetic look.
>"I'm sorry about all that. Let's just say that your meal's on the house, alright?"
>You nod, wondering absently if you should feel sorry for Noteworthy or envious for what is about to happen to him.

>It was a hulk-tastic kind of day.