Continuing the tradition of clothing TF: one of Rarity's friends is accidentally transformed into a literal cocksleeve and she decides to wear them for the day. This wouldn't be a problem, except Rarity won't stop staring at handsome stallions, making her full-sized erection difficult to hold.

Rarity eyed the stallion in front of her with no small amount of approval. She’d always had an eye for cute stallions—and mares—and this one was no exception.

She slid one hoof down her side, letting it fall into the curve of her flank. One had to make sure that they were prepared for a meeting with one of the opposite sex. With that said, she noted that the line for the bakery wasn’t moving forward any time soon, and so took it was an opportunity to ogle a bit more.

The curve of the stallion’s flank was almost as attractive as her own: taut, firm, with a slight evidence of the bubble-butt that more submissive stallions tended to hone. She stifled a giggle, then peeked around him—ostensibly to see the front of the line. But instead, she managed to catch a glimpse of his jaw: thick, rugged, with a well-molded coiffure and a neckline that spoke of just enough attention to one’s fitness. Her lower lip soon found itself quivering with desire.

At the sight of such a suitable specimen, Rarity’s cock began to perk up between her hind legs. She’d already been semi-erect, the feel of warm fresh air on her skin being enough to arouse her to a minimum. But the sight of this stallion’s tight, inviting rear, of his rugged, splendid countenance, was simply too much to keep things in polite company. Her own “stallionhood” swelled and throbbed, soon passing a foot in length and nearly half that in girth.

She wasn’t fully erect yet, though. A proper lady had larger, better equipment than that. Yet something held her back: namely, the bright blue cocksleeve that surrounded her member. The cocksleeve, one Rainbow Dash-turned-cocksock, would have blushed had she been capable. Instead, she merely groaned internally as Rarity’s thick, full member strained against her fabric.

Rainbow Dash made for a very comfortable cocksleeve, it turned out. Her soft, smooth threads rubbed pleasantly against Rarity’s member, only driving the mare’s arousal to even greater heights. But such a cocksleeve as Rainbow had been made into was meant for a stallion of a more moderate size. Ten inches in length and three in girth was about the extent of what Rainbow Dash’s new form could handle. But Rarity’s size wasn’t anywhere near so modest.

Rainbow Dash was stretching more than she could have ever prepared for (insomuch as anypony can ever prepare for being made into a sentient cocksock to be worn on a best friend’s throbbing, erect member). Rarity’s stallionhood was now reaching fifteen inches in length, with a circumference of nearly fourteen, and Dash was very much unprepared and overstuffed. Dash felt her threads being stretched even wider around Rarity’s massive member as it topped out around sixteen inches long, the tightness of the cocksleeve only serving to turn Rarity on even more.

Rarity herself eyed the stallion’s rump even more closely, licking her lips as the line stepped forward and she was able to see his rear creasing and flexing with his step. What a catch, indeed. She was able to catch just the barest glimpse of his stallionhood between his legs: a well-sized pair of balls, a bobbing, veined cock. Neither were anywhere near her own size, of course, but that was a price one simply had to pay.

A cocksleeve of Rainbow Dash’s size could cover most of a stallion’s member, all the way from the base to the flare. But on a mare of Rarity’s size, she barely even covered a third. Rarity’s nostrils flared as she imagined that stallion’s shaft penetrating her marehood, his balls slapping up against her rump as he rutted her mercilessly—or, perhaps, her own shaft penetrating his rear, her weighty, churning balls more than ready to spill their seed. She wasn’t picky.

Rainbow Dash just sat there around Rarity’s cock and groaned silently. She’d imagined being stretched by her friend’s fat cock more than once...but not like this.

Definitely not like this.