Mikey smiles with his whole body. When he is truly happy he radiates, broadcasts his emotions with every movement, every noise and every step, with a wide grin showing all his teeth and lighting up the room, filling it with his laughter and spreading to those around him.

Leo doesn't smile often but when he does it's a soft, quiet thing, subtle but full of meaning. He smiles with his eyes, his lips only curl slightly and usually it's barely a twitch but his emotions escape unchecked through his gaze. When he smiles, his eyes are full of I love yous and thank yous and he becomes silent, losing his ability to form words. His eyes shine a little brighter when they are smiling and you'd be certain he's about to cry but no one has ever seen it happen.

Don's default expression is a smile yet there are a million different meanings to the upward curve of his lips that often graces his features. Usually they are patient and gentle, disarming and soft. Sometimes they are wry and devious, sharp and biting, other times witty or excited. They form a language of their own which his brothers have become fluent in. His joyful smiles are usually secret, pulled from him unexpectedly and often hidden behind a hand accompanied by darkened cheeks. His laugh is a soft intake of air you'd miss if you weren't listening. On the rare occasion he does laugh unrestrained you want to wrap yourself up in the noise and hold onto it for the fleeting moment it's there before it's gone.

Raph chuckles often but it's usually sarcastic, a sharp gravelly noise expelled through equally sharp teeth and a crooked grin. When he does laugh in earnest it's loud, honest and unmistakable, his head thrown back and barked out. His booming baritone vibrates through your body and dispels any dark shadows in the room by its sheer force. He isn't embarrassed by the tears he sometimes wipes away from the corner of his eyes when he's left breathless afterwards and it is usually accompanied by strong slaps on the back if you are in range and a smirk in your direction with a playful gleam in his eye that lasts for hours.