Answer:
partially disclosed, personally liable.
Step-by-step explanation:
John is an agent to a partially disclosed principal because he didn't tell Wanda who Peabody is, he just told her that Peabody existed. This type of partial disclosure is common when the principal is someone (person or company) that is well known and specially wealthy. Although other reasons might apply, but the most common one is that the principal rears that his/her identity was known, the conditions for a contract would vary, e.g. an agent for Disney that is looking for land to build a new park will not disclose the principal's identity because they know that the price would increase dramatically.
In most states, John would be personally liable to Wanda because he didn't disclose Peabody's identity. If he had disclosed the identity of the principal, then only the principal would be liable. In any case, since John is acting on behalf of principal, Peabody is also liable to Wanda for the contract that John signs. It doesn't matter if the principal was disclosed or not, his/her responsibility is the same. E.g. if John and Wanda sign a contract, and Peabody doesn't perform, generally the third party (Wanda) would sue the principal because people assume the principal has more financial resources than the agent.