When cassidy gets angry he turns into shadow freddy but when cass gets really angry his disc overheats and misfires causing his appearance to become horrific and nightmarish

Which only happens when he's really lost his temper and is not thinking straight and has gone completely psychotic and calming him down is not super easy and freddy is desperately trying to calm him but he's worried cass might be lost to madness forever if he doesn't calm down

However what freddy and everyone else doesn't know is just how aware cassidy is when he's like this