>"Anonymous, REALLY, if you're going to have to do this, perhaps you could at least be-WAHAHA-!"
>Rarity's voice shifts several octaves as your weight presses down on her, shuffling to get comfortable on the saddle strapped around the pony.
>She trembles under your weight, bringing her head back up and making an attempt to walk.
>"I don't mean to be rude, darling, but you're... rather heavy."
>She grunts, just about managing to stretch her legs out, only able to walk at about five miles an hour.
"Giddyup!"
>"Oh, you can't be serious."
"Uh uh. Horsies don't talk. They ride."
>Before she has the chance to even attempt to protest, you bring the tight leather bridle from your pocket and fit it over her muzzle, the bit - a little black rod - fitting perfectly between her teeth.
>"Mmmmpph!!"
>With a yank you pull the bridle right and force her head left.
>She's restricted by the tight bands and buckles that press down into her skin; keeping her perfectly in place and completely at your command.
"C'mon, Horsey! You can take me over to that tree, right?"
>You pull her head in the direction of it, hearing a startled, muffled yelp from the unicorn as she makes an attempt to walk you over; still struggling under your weight but doing her best.
>Your hand trails down over her flanks, feeling where the fur grows slightly more fuzzy and silky on her cutie mark.
>You ready your hand and bring it down with an audible smack.
>Rarity squeals, rearing up before charging towards the tree, letting you jump up and down on her back as the canter becomes a gallop.
>You keep a firm grip on the back of the bridle, swinging your arm around to steer her one way and then the other, feeling her respond almost instantaneously.
>After the shock of your unexpected spank has worn off, Rarity reduces her speed and settles into a steady trot once again.
>Your hand reaches back to run along the tight buckles and straps that secure the saddle to her body, reaching along her rump and tightly pressing against her pussy lips.
>Your finger plays with those lips; slick and loose.
>Rarity groans disapprovingly, but she knows she's still ultimately at your will.
>Your thumb finds her ponut, rubbing that twitching ring of rubbery muscle.
>Her legs try to push together to contain her privates, but the strap won't allow her.
>Finally your thumb meets the dock that sits under her tail; tough but fleshy as you press down on it gently.
>She seems to react, a stuttering moan let out into the bit that's filling her mouth.
>You're done teasing her pussy, though; the poor mare has it bad enough.
>As you round another tree you pull Rarity over to one side of the path, dismounting and seeing her rise up into her usual stature.
>Her eyes are glaring at you with fiery, undying anger. 
"Would the horsey like a treat?"
>You tug on the bridle and allow the bit to pop out from her mouth.
>"Why, I have NEVER been quite so humili-"
"I said... would the horsey like a treat?"
>She pauses and just stares at you for a second. You produce a fresh carrot, wafting it in front of her to try and entice the mare.
>"Anonymous. This gross humiliation has gone on quite enough. Would you be so kind as to-"
"You want the bit again?"
>"No! I mean... oh, fine!"
>Her mouth opens, accepting the carrot and crunching it. She can't make eye contact with you though. She's far too angry and far too embarrassed.
>"Are you QUITE done?"
>Your hand parts her mane and gives it a ruffle, but you decide her torment has gone on long enough.
>You unfasten the bridle and saddle and immediately she's far more comfortable.
"Hey, what do you think the chances are of me slipping these onto Applejack while she's distracted."
>"Well, if you're particularly keen on having broken ribs I say go for it." She snarls, half-serious and half sarcastic.
>"I just hope now you have this... off your chest, you won't go doing it to me again anytime soon."
"I can't make any promises."
>She hits you with another pouty, fury-wrought glare.
"I mean... of course not, Rarity."
>"That's better."