Like most television shows, adding a kid can kill the show. Mork and Mindy did just this...with a twist. Their kid was Mearth and he was born an adult. Since Mork was not from Earth, things were different with the birth of their child. First off, Mork gave birth, or rather laid an egg and it grew and hatched Mearth, played by Jonathan Winters. The addition of Mearth would cause the decline of this Happy Days spin-off.
Mearth first appeared in the fall of 1981, which would be the start of the final season for Mork and Mindy.
Jonathan Winters who was one of Robin Williams' idols, had a wide and varied career, including his own TV show. Last we heard of Jonathan, he appeared in "The Adventures of Rocky and Bullwinkle".