Speaking parts ruin television

You’re watching your hour-long drama/mystery/police procedural show on television, and your heroes engage in conversation with a hitherto unknown guy or gal on the street, who just happens to be hanging around. Given that speaking parts pay much more than stand-around-and-nod-silently parts, you can bet your sweet plotline that the guy or gal had something to do with the drama/mystery/dead guy. It’s a dead giveaway, but what are you going to do? Spend more to have a lot of red herrings jabbering away? I don’t know. Do you have any suggestions?