"Let Me Be Your Star" in the Pilot. Probably the most thrilling moment in the series.
"Let's be Bad" from the episode of the same name. As Marc Shaiman, composer of the number, said...
"Note to songwriters: always have Megan Hilty and choreographer Josh Bergasse take your song and fly with it. As we filmed this number at a theatre on Staten Island we realized we were watching a number from a made-up musical, which was a song inspired by an actual movie, being performed in a real theatre while being filmed for a TV show. I think my head exploded shortly after having that thought."