Undisclosed principal: principal whose identity is totally unknown by the third party and the third party has no knowledge that the agent is acting in an agency capacity at the time the contract is made
a. undisclosed principal bound to perform just as if principal had been fully disclosed at time contract was made
b. agent entitled to be indemnified by principal—failure of principal to perform will make him liable
c. once disclosed principal's identity is reveal, the third party generally can elect to hold the principal or agent liable
d. undisclosed principal can require third party to fulfill the contract, unless

i. undisclosed principal was expressly excluded as a party in the written contract
ii. contract is negotiable instrument signed by agent with no indication of signing in a representative capacity
iii. performance of agent is personal to contract allowing third party to refuse principal's performance