It's A Bikini World was filmed in 1965, but not released until 1967, this may account for the fact that I had never seen this movie, since by 1967 I had lost interest (with most of the rest of America) in "Beach Party Movies". Tommy Kirk is the beach playboy and when he can't add Deborah Walley to his list of accomplishments, he disguises (well he wears a pair of glasses and dresses like a nerd) himself and pretends to be his own twin brother in order to win her over.
There was a pretty good line-up of music acts in It's A Bikini World: The Animals perform "We Gotta Get out of This Place," The Castaways sing their hit "Liar, Liar." The Toys perform "Attack," The Gentrys sing "Spread It On Thick" and Pat & Lolly Vegas (who would later morph into Redbone) perform "Walk On (Right Out of My Life)." Bobby "Boris" Pickett doesn't sing in the movie, but he has a supporting role as Tommy Kirk's best friend.
Tommy Kirk's acting really surprised me in this movie. People will
probably think I'm crazy, but Kirk reminded me of a young Cary Grant. He
would have been perfect in some light romantic comedies, but soon after
this film (except for some sporadic appearances) he left the world of
acting and for 20 years operated a carpet cleaning business. Even though the plot was light and silly (just as expected in a "Beach Party Film"), I thought It's A Bikini World held its own against the Frankie and Annette films of the same ilk. If, like me, you didn't catch this one the first time around, check it out now; I don't think you'll be disappointed.