The “Cats” composer played “Itsy Bitsy Teenie Weenie Yellow Polka Dot Bikini,” a spy tells us. “He was mouthing the words and having people sing along.”
Webber even got on the dance floor where he boogied with a number of women wearing cat ears.
Elaine Paige, the first Grizabella in “Cats” and original “Evita,” led the dancing with Sonja Morgan.
Over in Bemelmans Bar, Billy Stritch got on the piano to lead David Cromer, Katrina Lenk and casts of “Mean Girls” and “Frozen” in “New York, New York.”
Winners, including Andrew Garfield, Laurie Metcalf, Glenda Jackson, Lindsay Mendez and Justin Peck, mingled as the bash raged till 5 a.m.