I'm stating the obvious when I say that Bill is a master of disguise. The moustache is a brilliant touch, as is the fact that he added a second pen to his pocket.
Personally speaking though, I don't think the moustache and pen are necessary. Nobody is even going to be looking at Bill's face when he's wearing a pair of fancy pants like that.
(Pilot V5 Hi-Techpoint 0.5 Pen on 28lb. laser paper. Digitally coloured in Affinity Photo)