In 'Pretty Little Liars', who sends threatening messages to the girls?

In 'One Tree Hill', what sport is central to the story? In 'Friday Night Lights', what sport does the Dillon Panthers team play? Which actor played Coach Eric Taylor in 'Friday Night Lights'? In 'Dawson's Creek', in which fictional town is the series set? In 'Riverdale', which classic comic series inspired the show? In 'Twin Peaks', what does Agent Cooper famously love? In 'Northern Exposure', in which fictional Alaskan town is the series set? In 'Hill Street Blues', what does the sergeant say at the end of roll call?