History Film / FridayThe13th1980

** [[spoiler:Then again, she did specify she was the camp cook and was working when it happened. Jason was in the care of the counselors when he went swimming because his mother had to make a living.]]

** [[spoiler: Ned is an obnoxious jerk who nearly shoots Brenda with an arrow and fakes drowning as a prank; needless to say, viewers won't be sorry to see him go when Pamela suits his throat.]]

* DaylightHorror:
** [[spoiler:Jason's first onscreen appearance takes place in a nightmare that Alice has, where he attacks her in the middle of a lake]].
** [[spoiler: Annie]] dies in the middle of the day.

* FormulaWithATwist: ''Film/FridayThe13th1980'' copied the Slasher formula almost wholesale from ''Film/Halloween1978'', except set in a forest camp and make the killer's identity a MurderMystery plot point. Later entries in the series helped codify the genre with its undead villain, Jason.

* FormulaWithATwist: ''Film/FridayThe13th1980'' copied the Slasher formula almost wholesale from ''Film/Halloween1978'', except set in a forest camp and keeps the killer's identity a mystery. Later entries in the series helped codify the genre with its undead villain, Jason.

** This and ''[[Film/FridayThe13thPart2 Part 2]]'' are the only films in which they don't deliberately write unlikable heel characters to root the killers on. All the characters are generally nice people that treat each other kindly. A contrast to later entries where there's a few characters to root the killer on.

* FiveSecondForeshadowing: [[spoiler:Mrs Voorhees tells Alice that she's "not afraid" to go back to the camp about literally five minutes before she's revealed to be the killer, so of course she isn't afraid to go back.]]

* FormulaWithATwist: ''Film/FridayThe13th1980'' copied the Slasher formula almost wholesale from ''Film/Halloween1978'', except set in a forest camp and keeping the killer's identity a mystery. Later entries in the series helped codify the genre with its undead villain, Jason.

* HorrorDoesntSettleForSimpleTuesday: A triple-whammy as the movie takes place on the eponymous day, Jason's birthday, ''and'' on a full moon!

* {{Lunacy}}: When the Sheriff gives Steve a lift to the Camp Crystal Lake, they start arguing about whether or not a full moon has an effect on crime rates.

* SamusIsAGirl: A non-heroic example; [[spoiler: you'd be forgiven for thinking the killer is a young man at first, since she is initially only shown from the shoulders down, wearing a man's shirt and trousers. Then in the last 15 minutes of the movie, the serial killer picking off the counselors is revealed to actually be a middle-aged woman.]]

** The film uses SexSignalsDeayj to kill off the characters, but there's an in-story justification for it. [[spoiler: Jason drowned while camp counselors were fooling around, so hatred of any kind of sex is his mother's FreudianExcuse]].

** As famously pointed out by the opening of ''Film/Scream1996'', [[spoiler: the killer is ''not'' Jason, or any similarly hulking invincible man-mountain in a [[MalevolentMaskedMen creepy mask.]] The killer is not only female - something still rare to this day - but an unmasked, [[TheyLookJustLikeEveryoneElse totally ordinary-looking]] middle-aged woman with no scars or deformities. She doesn't even wear a scary costume, just a blue wool sweater-blouse and jeans.]]

* DeathBySex: This film probably made it a staple for slasher flicks. This is how Barry and Claudette and Jack and Marcie die. Justified since [[spoiler: Pamela]] is specifically targeting people who have sex, because that's how Jason drowned - two counselors who were supposed to be watching him were having sex instead.

** The film uses DeathBySex to kill off the characters, but there's an in-story justification for it. [[spoiler: Jason drowned while camp counselors were fooling around, so hatred of any kind of sex is his mother's FreudianExcuse]].

* AnAxeToGrind: Marcie is killed with an axe.

** This and [[Film/FridayThe13thPart2 Part 2]] are the only films in which they don’t deliberately write unlikable heel characters to root the killers on. All the characters are generally nice people that treat each other kindly. A contrast to later entries where there’s a few characters to [[RootingForTheEmpire root the killer on]].