He spends a solid minute working up the courage to knock. When he does, Leo hits the wood way too hard, wincing as his knuckles scrape the surface.
"Come in, dude!" Mikey calls. He sounds a little surprised. Leo's surprised too, to be honest. Surprised he was stupid enough to agree to this dumb bet, and surprised that he's following through on what he offered.
Leo knows full well that he could walk away from this if he wanted--Mikey might tease him for a little while, but it wouldn't be the worst thing in the world, and he'd forget it all soon enough. Still, he's never felt comfortable breaking his word to Mikey. And maybe, just maybe, a part of him is curious, not that he'd ever admit it in a million years.
He steps inside, carefully locking the door behind him and tugging to make sure it's secure. Mikey's casually sprawled across the sheets, legs spread enough for Leo to see his pink....undergarments.
Leo bites his lip. "You're wearing them too?" He knows his brother wears this stuff sometimes, it's how he came up in the ridiculous idea in the first place. He just didn't think Mikey would be wearing them right now. 
"What? Oh, yeah, the other stuff's in the wash." Mikey rolls gracefully to his feet and stretches, giving Leo a very good view of the--fine, he'll say it--panties. They're edged with little frills of lace that flutter ever so slightly as Mikey sashays across the room. God, Leo hopes he doesn't have to wear lace.
"Besides, I wanted to support you, big brother." Mikey opens the closet and fishes around, humming to himself. "You're taking a very big step."
Leo sinks onto the bed with a groan, rubbing his eyes. "Can we please get this over with?" he asks.
"Yeah, yeah." Mikey flops down besides him, holding out a bundle of cloth like an offering. "Your armor awaits, Sir Knight."
Leo wants to roll his eyes, but then he gets a better look at what Mikey's offering and he's too shocked to do anything, but stare. "Blue? Seriously?"
"What?" Mikey shakes the panties out "Blue goes well with your eyes, dude! It's basic fashion sense. I just want you to look good."
"I though you wanted to embarrass me?"
"That's just a side bonus. Now come oooonn...." Mikey waves the panties back and forth, eyes and big and round in that way he knows Leo can't resist. "For me, please? Pretty pretty please with a cherry on top and cream on the side and--"
"Fine," Leo says quickly, yanking the panties out of his brother's grip. They're a lot softer than he expected and he has to hold them carefully, worried he'll tear them in his massive fingers.
He's pretty sure they're bigger than whatever, um, size that April wears, not that he'll ever find out for sure, although they still look tiny compared to the rest of him. The blue is a bit darker than the shadow of his mask, which is a relief.
He brings them as close to his face as he dares and takes a cautious sniff. Nothing but that rare scent of clean plastic newness, the kind he didn't even know existed until they went topside for the first time. No sign of Mikey or any poor stranger he lifted them from.
"Seriously?" Mikey has the gall to look offended. "I lifted those right off the rack just for you, dude. You're the first princess to ever get crowned with 'em."
Leo sighs. "I don't like you stealing. And don't call me princess."
"Fine, whatever. It's all cool, I'll get Donnie to make a donation to the store from SORDID later on. Now, come on..." Mikey reaches towards his legs, but Leo pulls back.
"I can put them on fine, okay?" he says, maybe too quickly.
"Sure, dude," Mikey says, with a shit-eating grin. "Sure."
Leo huffs, setting back so that he can properly plan this. These panties feel so much more delicate than sweatpants and he really doesn't want to mess them up with his gigantic feet. Mikey got them for him, after all, and just because this is embarrassing as hell doesn't mean Loe wants to treat his brother's present this way.
"If you need help--"
"I'm fine!" Leo insists. He grits his teeth and carefully slips one foot, then the other, through the panties, sucking in a breath as the soft fabric brushes his ankles. He checks a few times to make sure he hasn't accidentally put two legs through one hole or something, then starts to very carefully drag them up his legs.
It's slow going, with a lot of embarrassing wriggling and pausing to make sure he's not messing things up. The audience doesn't help.
"You look like you're plotting an attack, dude. Chillax."
"I am chillaxed," Leo growls.
He has to kneel up off the bed to get them to his waist, tugging and adjusting until they're resting over his hips. Mikey lets out a soft sigh at the sigh and Leo flushes, folding his arms over his chest.
"Happy?" he mutters. The panties feel breathtakingly weird on him, a weird that shifts from good-weird to bad-weird whenever he tries to concentrate on it. He's never worn anything this soft before, and it freaks the hell out of him in a way he can't put words on.
"Always, bro," Mikey replies. He's looking at Leo in that way he gets sometimes while in bed with him and the others, eyes a little glassy with something that might be wondered. He starts to extend a hand, than pauses, looking uncharacteristically nervous. "May I?"
Leo sighs. "Fine." He's come this far, he might as well let Mikey grope him a little.
But his plan to be stoic flies out the window as Mikey's fingers drift across his hips, the sensation somehow, ridiculously heightened by the barrier between them. "Hold still," his brother murmurs, but Leo couldn't move if he wanted, muscles locked up as his brothers' fingers drift across his skin, tugging and pulling as he adjusts the underwear.
He's barely touching Loe at all, but there's a little curl of heat lighting up in Leo's stomach all the same. They're never this butterfly-light with each other, not even if in bed. It's...nice.
It's so crude and silly and goddam unworthy of a leader, and Leo shouldn't be enjoying as much as he should. Shouldn't be relaxing into the thought of being handled so gently, shouldn't be tempted by the sudden, ridiculous idea to waggle his hips, see if he can make Mikey blush for once.
But he keeps still until his brother finishes adjusting him and sits back with a sigh. "There," he says. "Feel better?"
He does, actually. "Yeah." Leo sinks carefully onto the pillows, carefully not looking down at himself. "So...now what?"
"Now?" Mikey's eyes flare with mischief. "Now we go see what you look like."
"Wait, what--" But Mikey's already dragging him off the bed and towards the mirror tucked in the corner. It's an old thing, scratched and with an irremovable ring of dirt costed at the edges, but Mikey still treasures it.
He pulls Leo to a stop in front of the mirror and gestures at him a la Will Smith. "Ta da! What d'you think?"
"I..." Leo looks at himself for half a second before yanking his gaze away. "What do you want me to say, Mikey? I'm a turtle in..." He waves at himself. "...this. It looks ridiculous."
"Really?" Mikey asks, sounding almost confused. "'Cause I think you look prettier than ever, dude."
Pretty? He's not pretty. None of them are. He's a scarred, hulking creature with green scales and bulging eyes and limbs that look ridiculously over muscled when set against this little scrap of fabric. "Don't be ridiculous," he scoffs.
"I'm not!" Mikey protests. "You look good like this, you really do." His hand brushes Leo's thigh, rubbing at the scales, and Leo's breath catches before he can stop himself. "Goes with your eyes, like I said, and it draws attention to those great legs of yours."
Great legs? He has great legs? He always assumed they were just--you know, legs. "I," he swallows, not sure what to say.
"I mean, you're no slouch on the regular," Mikey says, his voice suddenly going a little husky. "But when you're done up like this..." A very distinct, very familiar something bumps up against Leo's backside and he stiffens, feeling an answering shift between his own legs.
"You're good enough to eat," Mikey purrs. He reaches out and turns Leo's chin, forcing him to confront his reflection.
The turtle staring back looks red-faced and lost, hands twitching anxiously by his sides. The turtle looking back can't seem to keep his eyes off Leo's waist, because the panties really do seem to draw the eye there. The turtle looking back doesn't seem to know what to make of all this, but seems to have very clear feelings regarding the little brother clinging to him like a lustful anaconda.
An impulse takes Leo before he can stop and he turns his head, letting Mikey pull him into a kiss. And when Mikey reaches into the panties to touch him there, he doesn't resist.
Leo doesn't know if he really is pretty, but he know he likes the word, like the way it sounds in Mikey's mouth, the way it settles on his skin. He arcs into the word, into his brother's touch, unable to hold back a moan as Mikey gently nudges him back to the bed.
"Fucking hot," Mikey whispers, crotch suddenly bugling inside his panties as he drops down. A dark and forbidden part of Leo thrills at the obscenity in his little brother's mouth, and he follows suit, letting out another churr.
He moves to touch himself, but Mikey takes his hands and plants them firmly on top of his head. "Stay still, darling," he murmurs, grinding their crotches together.
It's so stupid, they're not even touching each other, but Leo feels Mikey, feels his size and his heat and his desire. The cloth ripples and tugs at sensitive flesh when they push together, somehow managing to heighten everything instead of reducing it. Their churrs rise together, melting into each other, a kind of communion deeper than anything they've ever had before.
Then Mikey's reaching down, hands slipping past both sets of underwear that so he's touching Leo with one and himself with the other. "Shell," Leo gasps, unable to help himself as Mikey rubs up and down, up and down.
"Stay with me," Mikey murmurs, his eyes a little glassy. "Stay with me, princess." For some reason, the name doesn't bother Leo as much as it should. now.
And he stays, for as long as he can. He grips Mikey's should and clings to the sensation of skin and fingers and impossible softness until he gasps, "Mikey," and his brother's pulling them both free, directing their release onto the bedsheets.
They slump down into each other's arms, the hard lines of the world blurring into a soft, peaceful haze. Leo reaches down and runs an idle finger along the lace of Mikey's panties. His brother makes a little happy noise at the touch, planting a sloppy kiss on Leo's neck.
"Was that good?" he murmurs, breath warm on Leo's air.
"Yeah, it was okay," Leo mumbles. He suspects that later he'll feel embarrassed and a little overwhelmed, confused at how quickly Mikey undoes him...but now, though, it just feels good.
"Good. So we can pose for pictures later, yeah?"
That jerks Leo straight back to earth. "No. No way."
"Please...."
"No, Mikey." He sure as hell doesn't want proof of this, whatever this is, floating around cyberspace. Especially in the hands of someone forgetful as his brother.
"Fine," Mikey lets out an exaggerated sigh, but his eyes are still soft as he snuggles up against Leo. "Killjoy."