When someone says they're turning one of the most beloved movies ever into a musical, there's always some cause for worry. The usual questions flood in: 'Will they do it justice? 'Will they say this line?' 'What are they going to change?' In most cases these worries are warranted, but in the unique case of Mean Girls, Tina Fey herself returned to adapt her modern teen classic into a hilarious and splashy musical comedy.