I don't know about any of the other names, but I wouldn't want to be called Mouthpiece. I think Etna-san would laugh at me.

Purple...oh, you must've met Mid-Boss-san! No, he's not evil at all. He's just funny. He keeps saying he can beat Laharl-san, but whenever they fight he just makes some strange excuse and runs away.

Oh, most of the demons in the Netherworld are actually pretty nice! They just don't want to admit it. Like Laharl-san - he keeps saying he's evil, but he really is nice deep down. He just doesn't want anybody to know.