Lily took to the stage as Princess Fiona and blasted out a rendition of 'I'm a Believer' as part of Children in Need's POP Goes the Musical fundraising event.
Watch Amelia Lily in Shrek:
The popstar said: "I've always wanted to perform on a West End stage, and Shrek The Musical is such a great show, it's a dream come true! I'm so happy to be part of BBC Children in Need this year, it's a fantastic cause."
POP Goes the Musical helps raise money for disadvantaged children and young people here in the UK by getting popstars to appear in West End theatre production.