Yes, she's going to appear in the episode the penguin who loved me as a major character. She is being voiced by Callista Flockhart
Yes dolphins do appear
Yes, they are sisters who appear to be not particularly close and they seldom, if ever, refer to one another in the media
Kowalski has a crush on Doris the Dolphin. She never appears but is mentioned in several episodes: Gone in a Flash, Driven to the Brink, Hot Ice, and a couple others.
Doris Davenport's birth name is Davenport, Doris.
Dolphin's commonly have an average intelligence. They appear to be smarter because they are playful, social creatures that humans can associate with.
Doris's
Kiss the Girls (1997) and High Crimes (2002).Dolphin Tale (2011)
doris
Doris Lytton's birth name is Doris Partington.
Doris Karnes's birth name is Doris Disbrow.
Doris Hume's birth name is Doris Hoeck.
Doris Doctor's birth name is Doris Bernheim.