It would depend on how you are doing your animation, wether your are deforming your model with bones and a skin or not.. But, the theory that you would need to figure out, would be to attach a "control" object(which would most likely be a hidden bone) to the back of the "character" and have its movement affected by your camera, thus when your camera pans right the character would "lean/twist" in that direction... If your are not using bones and a skin modifier to deform your model(ie, just using vertex manipulation), then you would need to animate the movement manually in your modelling package and just play it at the right time, when the camera is at certain angles to the character model.
Of course the actual mathematics of doin it will be complex, but its always best to work out your code yourself, otherwise you wont learn anything
Of course, the problem would be a little simpler to work out if you didnt want it to twist in the middle, I mean, its alot easier if you just had the rotation of your model fixed to your camera, so when the cam looks left, so does the model..
For examples of code doin all of the above things, do a forum search for terms like "animation control" "animating bones" "camera controls" and things like that, that should get you something useful.
If it ain't broke.... DONT FIX IT !!!
