On Dec. 2, 1968, a mysterious group of pompadoured cartoon faces turned back the clock of music history to highlight the golden era of doo-wop with their self-referencing album Cruising With Ruben & the Jets.

But before widespread head-scratching could ensue, record buyers who bothered to read the fine print found in a speech balloon on the cover art were informed that this strange ensemble of old-timers was none other than that “rocking teenage combo” the Mothers of Invention.

Even though just two short years had elapsed since Frank Zappa and the Mothers first burst onto the scene with 1966’s watershed Freak Out! album, the prolific bandleader and his charges had already churned out another pair of era-defining LPs filled with dark rock 'n' roll satire (Absolutely Free and We’re Only in It for the Money), and a daring avant-garde symphonic work (Lumpy Gravy), proving nothing was out of bounds for the maverick musical genius.

Certainly not the beloved doo-wop of Zappa’s teen years. He had dabbled with the music quite a bit before he became a star, both separately and alongside Mothers singer Ray Collins, who was convinced to hold off his inevitable departure from the fast-changing group long enough to help Zappa record this refreshingly straightforward collection of lovelorn pop ditties amid the continuing experimental nature dominating the concurrent Uncle Meat sessions.

The results may have sounded somewhat archaic when released in the thick of rock’s Age of Aquarius (or, if you like, well ahead of the nostalgia curve that led to George Lucas’ American Graffiti five years later), but innately infectious, and only mildly ironic puppy-love confections, like "Fountain of Love," "Later That Night," "Jelly Roll Gum Drop" and "Love of My Life" left little doubt of Zappa and band's authentic love, knowledge, respect and deep ties to doo-wop.

Not long after this one-of-a-kind release, the Mothers of Invention would resume their thoroughly modern, consistently groundbreaking recording activities, only sporadically returning to nostalgic sounds on random occasions in years to come. But for that very reason, Cruising With Ruben & the Jets has gone down as one of the most beloved and distinctive recordings in Zappa's incomparably vast and versatile musical canon.

See Frank Zappa Among the Top 100 Albums of the '60s