A character who speaks, but is for one reason or another unintelligible to the audience. A variant of He Who Must Not Be Heard. There are many possible reasons the audience cannot understand the character: muffled voice, thick accent, foreign language, very limited vocabulary, a robot communicating only in beeps. Other characters on the show frequently have no trouble understanding them, however. This leads to a lot of repeated dialogue that'd make little sense if we could understand both characters. ("Are we going to Dagobah?" "That's right R2, we're going to Dagobah!")