Halloween is usually when sci-fi, fantasy and horror TV shows take the terror up a notch. In celebration of this—and for the 7th of our 31 posts for the 31 days of Halloween—here are 51 of our favorite special Halloween episodes of beloved TV shows.

Oh Castiel! Why'd you have to go off and become God? On tonight's season seven premiere of the CW's Supernatural, we'll discover what happens after last season's shocker in which Castiel announced he was the new God and that the Brothers Winchester better bow down and start professing their love ... and fast.

It's premiere week the sequel, and, boy, is it busy as we get the season four (where's Peter?!) premiere of Fringe, a season seven (Cass is God?!) premiere of Supernatural, a season five (Penny and Raj?!) premiere of The Big Bang Theory and new series premieres of CBS's mathematical adventure Person of Interest and the ghostly A Gifted Man.

The CW really loves the cast of Joss Whedon's supernatural hit. It scooped up Sarah Michelle Gellar for her TV return in Ringer,...