If you had to reduce the Beach Boys to a single song, it might well by "California Girls." The song established the band's entire worldview: Los Angeles is paradise, and no place has women that are more beautiful. They opened roughly 26,000 concerts with the song over the past 50 years, because it sets the tone for the entire night. Brian Wilson wrote the song after experimenting with LSD for the first time, and it was the first song to feature new member Bruce Johnston. It was a massive hit, but not long afterwards Brian decided to move onto more complex material.
Twenty years later, David Lee Roth decided the song also perfectly matched his own worldview, and he cut it for one of his first solo efforts. The Beach Boys even helped out on the background vocals, and it again became a huge hit.