First, we created a scene containing the ThirdPersonController Standard Assets with the Ethan character. We were able to make use of the scripts and Animator Controller from the standard ThirdPersonController assets, but we changed the character the player sees to MaleDummy, which we imported from the Asset Store. Deleting or disabling the Ethan components in the Prefab meant that we don't see the Ethan 3D character model.
Adding a GameObject based on MaleDummy to our MyThirdPersonController Prefab placed a 3D character model in our Prefab. In order for the MaleDummy model to be correctly animated, we needed to ensure that the Animator Controller is targeting the Avatar (virtual skeleton) of the MaleDummy model, which we updated in the Inspector window.
The Animator Controller was then able to apply the animations (idle, walking, turning, running, and so on) to the MaleDummy character when directed to do so by its scripted components...