John Mason was a notable humanoid comedian.
In 2365, Data attempted to create a comedian to help him better understand the concept of "humor". Mason was among the holodeck program files that were contained aboard the USS Enterprise-D. The program list code for this comedian was ZB-45234. (TNG: "The Outrageous Okona", okudagram)
This character was only mentioned in writing.
This character was named after producer John Mason. (Star Trek: The Next Generation Companion (2nd ed., p. 70))