Teller speaks, and there is a 'Teller voice', despite his silence on the Penn and Teller show. This list of times you hear Teller speak ranges from Dharma & Greg to Miami Vice, believe it or not. Just pay close attention and you will hear the man with no voice speak. Source: http://en.wikipedia.org/wiki/Teller_(magician)#Teller_speaks.
Teller plays an anthropomorphic cat, Mr. Boots, on an episode of Dharma & Greg.
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He speaks in a guest starring role on the "Like a Hurricane" episode of Miami Vice in 1987.
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In the 1987 movie Long Gone, Teller played the son of Henry Gibson (whom he strongly resembles) and deliberately imitated the strong Southern accent Gibson used in the film. Gibson and Teller are both originally from Philadelphia.