"Where or When" is the first number to appear in the original Broadway production of Babes in Arms. The musical opens in Seaport, Long Island, on a hectic morning that finds most of the adult population embarking on a five-month vaudeville tour. Soon after his parents' departure, twenty-year old Valentine LaMar (played by Ray Heatherton) discovers at his doorstep a young hitchhiker named Billie Smith (played by Mitzi Green). Instantly smitten, he engages her in a discussion of movie stars, self-defense maneuvers, and Nietzsche's theory of individualism, at which point Val impulsively steals a kiss. Both admit to a powerful sense of déjà vu and sing "Where or When" as a duet.MGM bought the screen rights to Babes in Arms in 1938, and the following year the studio released a film with that title, starring Mickey Rooney and Judy Garland, that bore little resemblance to its stage predecessor; the characters and plot were substantially revised (by ten studio writers), and only two numbers were retained from the score. "Where or When" was one that survived, appearing 37 minutes into the film, sung by Betty Jaynes, Douglas McPhail and Garland in a scene depicting a rehearsal sequence, although Garland is cut short during her performance.
The lyrics of Where or When illustrate a memory anomaly known as déjà vu: 
"It seems we stood and talked like this before.
We looked at each other in the same way then.
But I can't remember where or when...
Some things that happen for the first time
Seem to be happening again."
The line "Some things that happen for the first time..." is often misunderstood or misheard as "Some things that happened for the first time..." which changes the meaning. Rather than recalling past events which actually "happened", the lyrics refer to present events which "happen" for the first time, but which falsely seem to be recurring.