Six months ago, someone made a fake Sarah Silverman Twitter account. But this seems genuinely to be the comedian's work, what with all the facetious jewish jokes and invented profanities. (Click for highlights.)
The hidden cuss at left, by the way, is "Redonkeydick." Only 41 posts and Silverman's already been censored by Twitter.
(For some reason Silverman hasn't linked to the the re-release of her 2004 mockumentary "Pilot Season." It's pretty good, for a free eight-minute internet thing!)