Katy Perry

Self

Shannon Woodward

Self

Rachael Markarian

Self

Glen Ballard

Self

Kesha

Self

Lockhart Brownlie

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Anthony Burrell

Self

Lexie Contursi

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Brandee Evans

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Bryan Gaw

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Scott Myrick

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Johnny Wujek

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Adele

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Jessie J

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Rihanna

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Justin Bieber

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Rebecca Black

Self (archive footage)

Alan Carr

Self (archive footage)

Darren Criss

Aaron Christopherson (archive footage)

Ellen DeGeneres

Self (archive footage)

Whoopi Goldberg

Self

Erica Hill

Self (archive footage)

Lucas Kerr

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Heidi Klum

Self (archive footage)

Avril Lavigne

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Bonnie McKee

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Alanis Morissette

Self (archive footage)

Dermot O'Leary

Self (archive footage)

Britney Spears

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Russell Brand

Self