I had to try this and it's very simple to do.
Open the uhp file of the skin in question and make a few changes.
(Save the original file to another location first!)
Taken from my Tall3 skin for the full body girl, I made the following changes in about 30 seconds...
;Coordinates of Animated Character
SkinFaceX=0
SkinFaceY=0
skinFaceWidth=0
skinFaceHeight=400
I ended up with a large blank skin with no Haptak character...only text. By limiting the size of the animated character, it effectively prevents the character from displaying.
It would be easy to create a "text only" skin for Hal but half the fun is chatting with the Haptek characters and enjoying their reaction, expressions and emotions. IMHO it only adds to the experience of chatting with an AI. To each their own.