their big silver metal knob right over their mouth for their helmet in their new skin- it goes up with their mouth, how it normally would if they didn't have the skin, and it looks unatural because, well, part of their helmet is detaching and acting like their mouth, so....
i tested this in the emote tab in the curio cabnet.
Steps to Reproduce
go to curio cabinet emotes make WX-78 your sample character (with gladiator skin) click fist shake emote
go to curio cabinet emotes make WX-78 your sample character (with gladiator skin) click fist shake emote