20 of 30
"Pretty Little Liars"
Number of episodes: 71 and counting
Apr. 18, 2013
The entire show revolves around a central mystery: Who is A, and why is he/she tormenting the main characters? Not only does a marathon mean you don't have to wait as long for answers, but the total insanity of "Pretty Little Liars" is wonderfully enhanced by concentrating your viewing experience.