When "Actors" use a prefix instead of a first name

Periodically, I've come across game shows, documentaries, or children's shows where people are credited on-screen with a prefix title and their last name, but no first name (Mr. and Mrs. Decker, Prof. Blow, Dr. Doe, Officer Schmo). They are on the episode, involved and interacting with the host/main character, and they are clearly identified, but their first name is not said or listed. What is the proper way to enter them into the system so that they can be credited properly on the episode's credits? IMDb policy is to drop and ignore the prefixes, but you can't just list Decker (I), Decker (II) in the credits, and omitting people credited on-screen screws up the credits.

Suffixes and Prefixes

Courtesy titles like Mr., Dr., Sir, [...] are not considered part of the name, and are not included in the primary name, even if that is how the name appears on screen. [...] (Exception: In the silent era, it was not unusual for women to be credited as, i.e., Mrs. John Smith -- in such cases, Mrs. is an integral part of the name, since John Smith is an entirely different person.).

When first names can be found elsewhere I get that you add them and do an (as Prof. Blow) attribute. But that isn't always the case.