Since I can't make playermodels for stuff, I made a large invisible bot mount a headcrab model onto it. It behaves like a headcrab in the sense that it can walk slowly, but it generally gets around by leaping about. With a certain RTB preference on, it can 'latch' onto players, rendering them completely unable to control themselves while they're 'spying' themselves. The headcrab causes the victim to aimlessly zig-zag about in random directions. If the victim somehow manages to die in this predicament, the headcrab and dead victim convert into a headcrab zombie (this also applies to headcrabs that somehow manage to collide with a recently killed player). Headcrab zombies produce headcrabs upon death if they get killed without damage taken to the head.
Headcrabs can also do this to bots. If headcrabs convert Combine Overwatch bots, they become Zombines. They have robotic voices, they're faster, they randomly charge at you, and they, at random, (however, with an increased chance depending on whether their health is low) they flail a live HL2 grenade about in the air whilst charging at you.
The only problem is that it's hacky as hell and somewhat disorganized and Frankenstein-esque in code.
