I've seen this done in several planes and there are a couple of ways to do it.

The way I would do it would be to mount a micro servo IN the pilot with it's head glued to the round servo wheel with "GOO" or silicone paste (so the head can be removed if necessary). If you want it to work with the rudder, just Y-harness it to the rudder servo.

Another way would be to mount the head on a vertical rod (torque tube) with a 90 degree bend on the bottom, a push rod would then connect the end of the bend to the rudder servo.

My friend used the mechanical version in his bi-plane, when the rudder moved right the pilots head would look left...

If the pilot is big enough you could also activate an arm to raise as if waving or giving the finger...

P.S. Is Castle still on this year? I've heard rumors their moving it.