The FXX network plans a marathon telecast this summer of Simpsons episodes—all 552 of them, consecutively. The network said yesterday the marathon will start Aug. 21 and continue into Labor Day. FXX programming chief Chuck Saftler said it coincides with the network's purchase of rerun rights and the development of an app that gives access to every episode of the long-running animated series. This fall, FXX will show four hours of episodes every Sunday, up until the time a new episode is aired in prime time on Fox. (More The Simpsons stories.)