Plo Koon

he wears a gas mask because jimmy didn't quite fix his mouth (he over corrected)

Early Life
Plo koon was molested by Jimmy saville on his child rape funtime bus and they mutilated him so badly that he had to wear a gas mask because they surgically attached other child's penises to his face.

he  contracted a space STI so the childs penises which used to hang proudly from his face now look like orange withered chillies, so he wears the gas mask partly out of medical need but also partly out of shame. He is ashamed that the childs penises attached to his face are no longer plump and pink but sadly shrivelled and droopy, much like darth sidious's penis.