The orange kitten from the MTM closing logo which is shown at the end of The Mary Tyler Moore Show, Rhoda, WKRP in Cincinnatti, and other MTM shows.
Mimsey can be dressed in different costumes. He's dressed as a surgeon on St. Elsewhere, and a police officer on Hill Street Blues.
from Jaberwocky poem in Alice in Wonderland by Lewis Carroll. Thought to mean misty and whimsical.
not to be confused with mimsy - flirtatious girl or female genitalia!
"all mimsey were the borogroves"