I'm not sure if the title of this thread is clear or not. The idea is choose an actor who either starred or was a regular/extensive recurring role where the character they played in one show morphed to a similar character in the other show. The roles could be progressive or regressive

A couple of examples.

Regressive example:
Mickey Dolenz played a circus boy in The Circus Boy. Then he morphed into a monkey in the Monkees

Progressive example:
Gavin MacLeod was a seaman in McHale’s Navy then morphed in to the captain of The Love Boat.