Spiderman calls Mysterio "chrome dome" despite the fact he never appears in costume.
When we last saw Mysterio out of costume, in Season 1 episode "The Menace of Mysterio" he is a short man with a bowl hair cut, pointed ears and normal skin color.
Mysterio appears out of costume in this story, he is a tall man with red hair and green skin, It's as if he was supposed to be a new character but changed at the last moment.