Season 19, Episode 18
The Simpsons spend the week at the Sundance Film Festival after Lisa's film documentary about every day life is accepted. Sponsored by Principal Skinner and Superintendant Chalmers, she is commissioned to make a similar film about her family. When the project is shown before an audience it is revealed that she has deliberately made it look like her family is dysfunctional in order to gain a popular vote by the public, which doesn't go down well with Marge.
*Read a more detailed summary for this episode on Wiki Simpsons