Plasma is a human that had an accident in the hospital during his birth - millions of gaseous plasma atoms were released into his body system which resulted in Plasma having special powers. However, his voicebox was damaged and he has to use sign language all the time during conversations. Plasma has a hired helper that helps people understand what Plasma's saying. He can read people's lips from special education and he can also read 3 different languages.
Plasma's looks: http://dreamself.me/d/giFs