Skinwalker/Mimic mod

Me and my friends love horror and chaos in GMod, and I'm wondering if there's a mod (NextBot or NPC) where something mimics a player — like takes someone's model and name — and acts like one of us, but it's secretly hostile. Like a skinwalker or doppelgänger vibe.

Something that blends in with the group until it suddenly snaps and attacks, or maybe stalks players pretending to be one of them.

Does anything like this exist on the Workshop or elsewhere?
Even a scripted mod or something experimental would be amazing.
Thanks in advance 🙏