In February of 1968, the Beatles gathered in EMI Studios to shoot a pair of videos for their song “Lady Madonna,” their first single of that year.

Back then, of course, they weren’t called “music videos,” but instead “promotional films.” And as was often the case with the Beatles, the original plan turned into something else.

At first, the idea was to film the band miming to “Lady Madonna,” but ultimately the Beatles decided to use the studio time to record an entirely different song, “Hey Bulldog.” This is why, if you pay close attention to the video, you’ll notice the images of the band playing and singing do not match up with the lyrics and instrumentation of “Lady Madonna.”

“The group were on a roll as far as recording was concerned and didn’t want to lose a day,” film producer Denis O’Dell recalled in his book At the Apple’s Core: The Beatles From the Inside. “Rather than mime for the promo film, they asked us instead to film them recording a new song they were working on at the time. The song, a forceful rock number written predominantly by John, was called ‘Hey Bulldog,’ and that’s the song that audiences saw in the clip. We tried to edit the footage so that it echoed the rhythm of ‘Lady Madonna’ (which wasn’t too difficult since the songs have roughly similar tempos), but if you’ve ever wondered why that promo isn’t lip-synched now you know!”

There were actually two films made, similar but with slightly different clips. In the second film below, you’ll notice a section devoted to, of all things, George Harrison eating a plate of beans.

In the end, the film premiered on the BBC’s Top of the Pops show on March 14, 1968. And no one appeared to bat an eye at the footage.

“Paul was a bit annoyed, but John was like a bulldozer that day, and the decision stuck,” engineer Geoff Emerick said in his book Here, There and Everywhere: My Life Recording the Music of the Beatles. “The sounds of ‘Lady Madonna’ would therefore accompany footage of the Beatles’ recording the new Lennon song ‘Hey Bulldog,’ and nobody seemed too bothered about that. They knew that most viewers wouldn’t even notice that they were in fact playing a completely different song, and they were right.”