Proof that all a horror series really needs is a good shock ending to its first film in order to root itself in the moviegoing consciousness. The original Friday the 13th is a woefully bad low-budget slasher flick, complete with a requisitely inept cast (including Kevin Bacon in uncomfortably tight shorts); laborious pacing; and an interminable catfight climax. That battle is between Adrienne King, as the lone survivor of a bloodbath at Camp Crystal Lake, and Betsy Palmer, as deranged serial killer Mrs. Voorhees. Voorhees is avenging the drowning of her son Jason some 20 years earlier, when he flailed about in the lake while the counselors were busy getting busy. (Friday the 13th is another sex = death horror picture. When the victims aren’t immediately poistcoital, they’re fresh off of playing strip Monopoly.) The reason the series lasted, though, is its penultimate scene, in which the rotting corpse of Jason rises from the lake to snag the seemingly safe King. Let the hockey games begin…