Mary Poppins Returns is now playing in theaters everywhere, and if you caught the Disney musical over the holiday weekend, you likely noticed the biggest production number revolved around the song “Trip A Little Light Fantastic.” A new Mary Poppins Returns featurette goes behind the scenes to show you how much work went into making this number a reality.

Mary Poppins Returns Featurette

“We’ve been preparing this number for over a year,” Mary Poppins Returns director Rob Marshall tells us at the start of this featurette, immediately setting up how complicated and tricky this all was. Lin-Manuel Miranda, who plays Jack in the film, and sings the “Trip A Little Light Fantastic” song, adds that the scene required “everything of everyone,” and Mary Poppins herself, Emily Blunt, calls the scene a “huge dance number” with close to 50 dancers.

And if dancing isn’t enough for you, there are also…BMX racers? Riding their bikes for some reason…? I don’t think anyone saw that coming, honestly. But here we are! Whatever you think of Mary Poppins Returns, it’s clear that Marshall and company worked hard to capture some sense of cinematic magic, particularly in this big, difficult production number. Just watching this featurette exhausted me, and I didn’t have to leave my chair. I can’t even imagine planning this for a full year, and then executing it. Good work, Mary Poppins Returns.

In Mary Poppins Returns, magical nanny Mary Poppins (Blunt) is back “to help the next generation of the Banks family find the joy and wonder missing in their lives following a personal loss.” Lin-Manuel Miranda plays her friend Jack, “an optimistic street lamplighter who helps bring light—and life—to the streets of London.”

The rest of the cast features Ben Whishaw as Michael Banks; Emily Mortimer as Jane Banks; Julie Walters as the Banks’ housekeeper Ellen; Pixie Davies, Nathanael Saleh and Joel Dawson as the Banks’ children, with Colin Firth as Fidelity Fiduciary Bank’s William Weatherall Wilkins; and Meryl Streep as Mary’s eccentric cousin, Topsy. Angela Lansbury appears as the Balloon Lady (who??), and Dick Van Dyke is Mr. Dawes, Jr., the retired chairman of the bank now run by Firth’s character.

The Mary Poppins Returns music score comes courtesy of Marc Shaiman, and the film features all new original songs with music by Shaiman and lyrics by Scott Wittman and Shaiman. Marshall directs a screenplay by David Magee, with a screen story is by Magee, Marshall and John DeLuca.