ET spoke exclusively with Streep at the London premiere of her new movie musical, where she dished on working with the iconic singer and teased her upcoming role on 'Big Little Lies.' 'Mamma Mia! Here We Go Again' hits theaters on July 20.
ET has an exclusive look at the filming of the sequel's first musical number, 'When I Kissed the Teacher.' 'Mamma Mia! Here We Go Again' opens in theaters July 20.