Scoutmob co-founder Michael Tavani said the Atlanta-based company has spent almost nothing on marketing, with word of mouth spreading the app's popularity in the 12 U.S. cities where it's available. ( Scoutmob's website shows a 13th that will be familiar to fans of "The Simpsons, " the fictional Springfield).

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She made a vocal appearance on the animated series "The Simpsons" in the memorable "Last Exit to Springfield" episode.

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He belongs to a group called the Simpsons Collector Sector and said he had a hard time convincing people he really did live in Springfield.

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