In
season 2 of
Star Trek: The Next Generation, the actress
Gates McFadden, who played
Dr. Beverly Crusher, became pregnant and a one-season replacement was needed.
Diana Muldaur, who played a one-episode character on
ToS, was called up. She played her role with a lot of...
bile, I think would be the best way to describe it.
No one has ever said anything positive about Dr.
Katherine Pulaski. Her character apparently got a crush on
Commander Riker's dad
Kyle Riker at some point in the past.
If you want to learn more about this character, I suggest http://archives.strek.com/pulaski.htm .