| Episode credited cast: |
 | Samantha Barks | - | Herself - Potential Nancy |
 | John Barrowman | - | Himself - Judge |
 | Daniel Boys | - | Himself - Performer |
 | Jessie Buckley | - | Herself - Potential Nancy |
| Arthur Byrne | - | Himself - Potential Oliver |
| Alexander Hockaday | - | Potential Oliver |
 | Barry Humphries | - | Himself - Judge |
| Ben James-Ellis | - | Himself - Performer |
| Jordan Li-Smith | - | Potential Oliver |
 | Andrew Lloyd Webber | - | Himself - Chief Judge (as Lord Andrew Lloyd Webber) |
 | Graham Norton | - | Himself - Presenter |
| Jodie Prenger | - | Herself - Potential Nancy |
| Karl Schmid | - | Himself |
| Harry Stott | - | Himself - Potential Oliver |
 | Denise Van Outen | - | Herself - Judge |
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