As influenced by "Beatlemania" and "The British Invasion of 1964", rock groups were the latest trend, putting many solo performers at a disadvantage. With the box-office success of A Hard Day's Night (1964) and the expected success of Help! (1965), three band member buddies--played by Gary Crosby, Jimmy Hawkins and Joby Baker--were added to to the plot in order to enhance the film's appeal to a "newer' generation of rock fans and "teenyboppers".
The song "The Meanest Girl in Town" was one of the only songs not composed for this movie. It had been written for Bill Haley and the Comets and recorded by then in 1964 under the title "Yeah She's Evil".
Even though the film is set in Fort Lauderdale, Elvis did not film any scenes in the city (as was common practice in later Presley films). Primary shooting was done at the MGM studios in Hollywood, while the beach scenes were filmed in southern California. Only second unit filming was done in Fort Lauderdale.
When Rusty is backing the boat trailer up to deliver Valerie (and Romano) to the motel, the frames are segmented resulting in a jumpy image. This is because Rusty is actually driving forward and the film has been reversed.
For reasons unknown, several of Elvis Presley's songs are slightly sped up, making his voice sound higher than usual. This is most noticeable on the title track. This error appears to have originated in the recording studio, as the RCA soundtrack album retains the sped up versions of the songs. A recording of "Girl Happy", mastered at the proper speed, would not be released until the 1990s. The explanation came afterwards that it was intentional and that it was supposed to give the title track an upbeat feeling that it lacked apparently in the original version. It has to be reminded that this soundtrack was recorded at the height of Beatlemania in June 1964 and that the record company tried to give some "extra-youth" to Elvis by speeding up the tape. Also, 1964 is the first year Elvis did not reach the TOP 10 with any of the six singles he released that year.