Peter and Olivia get caught up in a mysterious and musical tale on the April 29, 2010 episode of Fringe. It's titled "Brown Betty."
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This is a scene from "Brown Betty." It's a unique Fringe episode in which the characters perform musical numbers.
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This may seem hard to believe, but the April 29 episoe of Fringe will be musical-based. This is a shot of Olivia from it.
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Fringe Season 2 Episode 19 Quotes

You can tell a lot about a person by the music they listen to.

Peter

Must be nice to know who you are, to know your place in the world.

Peter