Mickey was a rat.
Biography[]
In the year 2267, Hikaru Sulu kept him with the intention of adding him to a zoo. When the crew of the Federation starship USS Enterprise became quite bored, Leonard McCoy taught Mickey to dance. When the crew saw this, he and Spock convinced the crew that this was a sign of bubonic plague. The mission to execute Mickey soon became known as Operation Mickey. Nyota Uhura penned the song The Saga of Mickey the Space Rat to commemorate this rodent. (TOS novel: Mission to Horatius)