Alright, so I was fooling around with Model Manipulator, and I decided to try and switch a citizen model to the infected models from L4D. Surprisingly, the special infected seem to perform animations of some kind before they T-pose. As in, the tank begins to do some weird flexing animation, the hunter goes into its crouch pose, and the smoker does its usual slouch.
Even the common infected had a brief animation, though I lagged majorly.
What exactly is going on here?