Final answer:
In the given context, Sam Superstar would be a partially disclosed or semi-disclosed principal because Angie Agent is negotiating on his behalf but has not revealed his identity to the third party.
Step-by-step explanation:
In the scenario described, Sam Superstar acting through Angie Agent is a disclosed principal. However, since Sam Superstar prefers to remain anonymous, he is not fully disclosed, thus making him a partially disclosed principal or a semi-disclosed principal. This term pertains to a situation where an agent reveals that they are working for a principal, but they do not reveal the principal's identity. A fully disclosed principal is one whose identity is known to the third party at the time the contract is made, while in the case of an undisclosed principal, the third party is unaware of the principal's existence. Hence, the key aspect is whether the third party knows they are dealing with an agent who is contracting on behalf of a principal.