How do you add a fixed joint to a first person controller

Is there a way to add a rigidbody a the first person controller prefab? When I do, the controller falls up. I tried to attach a script to the object in which I am attaching so that it has the same rotation and position as the controller but I am having problems. Can someone either tell me how to attach a rigidbody successfully, or post a script for how to do this? Thanks! Here's a snail for you help!