The title character was based on the author's daughter, Kathy Kohner-Zuckerman, and her adventures growing up in the surf culture at the beach in Malibu during the 1950's. She is still petite, healthy and attractive and lives in Pacific Palisades with her husband. And yes, there was a "Moondoggie", who lives in California and is an artist.
The producer wanted Elvis Presley to play the leading male role but the studio declined because Presley was at the time too expensive.
Cliff Robertson grew up in La Jolla, California, where he is well known for his surfing ability. Robertson can be clearly seen surfing in the movie. However, in a 1978 interview on 60 Minutes (1968), Tom Laughlin admitted he suffered tremendously during the surfing scenes.
Because of the widespread popularity of this movie and the book it was based on, the real-life Gidget, Kathy Kohner, was ranked number 7 in Surfer Magazine's 40th anniversary issue's list of the 25 Most Influential Surfers of All Time.
James Darren, Cliff Robertson, Tom Laughlin, and Doug McClure all appear bare-chested in this movie. In fact, Robertson's many shirtless scenes, showing him sun-bronzed and sweaty, easily constitute the best "beefcake" of his long movie career. Unfortunately, the normally very hairy chested James Darren was forced to submit himself to a complete body waxing which seems unnatural and out of keeping with his personality.