“Lamplighters are this magic presence bringing light into the darkness,” says director-choreographer Rob Marshall of the role of the “leeries” in his original movie musical Mary Poppins Returns.

Lin-Manuel Miranda plays the star lamplighter of the film, Jack, who reaches a new level of wow in the showstopper “Trip a Little Light Fantastic.”

The Hamilton creator and star revealed how he had to master the number: “My first day of rehearsal, when I first spun around the lamp post, [I thought], ‘How am I gonna do this?’ I practiced for weeks.”

Aside from the athletic choreography—reminiscent of “Steppin’ Time” in the original Mary Poppins—Marshall also brought in daredevil athletes. “The best BMX riders in Europe doing tricks amongst the dancing!” exclaims star Emily Blunt.

For all the hard work, Miranda ensures, “We're having the time of our lives doing that number.”

Watch the full video above.

Mary Poppins Returns opened in cinemas nationwide December 19 from Walt Disney Studios. The film stars Blunt, Miranda, Emily Mortimer, and Ben Whishaw, with appearances by Meryl Streep, Dick Van Dyke, and Angela Lansbury.