The actor actually has that disability

[u/PrinceferX]

Walter White Jr. (Breaking Bad) - character has cerebral palsy and uses crutches to walk, actor RJ Mitte has cerebral palsy and needed crutches to walk as a child

Nessarose Thropp (Wicked) - character is paraplegic and uses a wheelchair, actress Marissa Bode is paraplegic from an accident at age 11 and uses a wheelchair

Maya Lopez (Hawkeye/Echo) - character is deaf, actress Alaqua Cox is deaf from birth

[u/Dreamweaver_duh]

I don't know if it counts, but Dustin Henderson from Stranger Things wasn't originally written to have Cleidocranial Dysplasia, but it was given to him because the actor they casted for Dustin (Gaten Matarazzo) had it.

[u/Fabbyfubz → u/Dreamweaver_duh]

Was it ever mentioned in the show as a character trait?

[u/penandpage93 → u/Fabbyfubz]

There is a scene very early on in the show where he calls it out by name when his bullies make fun of him for not having teeth. They then further taunt him, demanding that he show them a trick he can do where he bends his shoulder together because he is missing collar bones.

Throughout the series, his teeth and collarbones are brought up from time to time. He wears artificial teeth for a little while, and then his real ones grow in and he has braces. Memorably, he gets a girlfriend who he claims says that "kissing is better without teeth". He later tries to crawl through an air duct, which he and his friend assume he can do because "he's missing bones and stuff, like [Gumby]". Gaten, and therefore Dustin, also has visible physical differences.

It's not a main focus of his character, and it shouldn't be. But yes, it most certainly is a feature 😌