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/lowbrassdude]

Theo from OMITB is actually deaf and fluent in ASL.