From the series finale, "The Last One" (#7322, May 25, 1988), which revealed that the entire 6-year saga of St. Elsewhere was the biggest joke in American Television history: a figment of young autistic son Tommy Westphall's imagination! :-O
During the end credits, you can see Mimsie the MTM Cat hooked up to life support; at the end of which, he flatlines and dies. This is a tribute as well as a farewell to Mimsie (a.k.a "Dick Turpin" and "Dick Marino"), who cashed in his 9th life in real life not long before (1968-1988).
Here's to ya, Mimsie.
You and your many logo incarnations have helped shape an intense TV icon for 26 years and counting. Mary Tyler Moore couldn't have picked a better mascot for her company.
We miss ya, old chum. <|,-(