Say you're making a time travel movie. (Nevermind how.)
When it comes to time travel movies, there are definitely tropes that moviemakers tread again and again, but usually it's for good reason.They work, if done correctly. Heck, Back to the Future, which celebrates its 30th anniversary today, somehow made a mom's attraction to her son hilarious rather than super creepy. Why? Because they relied on time travel tropes. And so can you. So take note, fellow filmmaker:
1. Time travel movies are reliant on good timing, where a single moment can change whole character arcs and lives.
This means you can create a whole plotline based on a character being late for some transportation or application deadline or meeting the right person at the wrong time. Forget the fact that our personalities, careers, and relationships change and develop over long periods of time. The first impression is the last impression in time travel.
Main character: Oh man! I missed the bus!
[cue sequence of how, if they'd gotten on the bus, the main character would've discovered the key to all existence, met the love of their life, and also lived forever, somehow]
MC: Oh well, I guess I'll just wait for the next one.
[cue sequence of main character's life, which is full of unrepentant misery and the existential feeling that they're always a step behind]
2. Family matters in the grand scheme of things. Your parents' past and your future children are directly related to your present life.
Obviously, this is generally true IRL. You wouldn't exist if your parents didn't meet, or at least if that particular egg and sperm didn't meet. But in time travel, your parents' whole past defines your wholelife. Also, when it comes to your children, it turns out the mother/father of your kids could be who you least expect, and "fate" is an amazing aphrodisiac.
Main character: My parents met at a high school dance!
[goes into the past and accidentally destroys high school]
Main character: Well, crap.
Main character: I hate you! You're dumb!
Romantic interest: Well, I hate you and you're dumb!
[MC and RI glare fervently at each other]
Time traveler: Haha, your children are going to find this hilarious.
[MC and RI give each other sidelong glances]
3. In time travel, one can "romantically imprint" on another character, if done correctly.
This might mean going in and out of their lives to the point that they've known you all your life while you've only hung out with them in the past fifteen minutes (see: Doctor Who, the Terminator movies). But it also tends to manifest when a man changes his present by going into the past and a woman changes her present after seeing her future (see: Hot Tub Time Machine, 13 Going on 30). This is somewhat supported by this observation on how men have love regrets and women have future love ideals.
Random hot dude: I'm here to tell you in the future you are literally an amazing goddess akin to the Madonna, but more BAMF.
Lady: Yes, this makes perfect sense.
RHD: Also, I'm already in love with you because of the stories and tales of how perfect and badass you are.
L: Finally, somebody who gets me.
Dude: [as he arrives in the past] Ah, I remember this place! This is how I met my ex-wife!
Hot lady he's never met before: Wanna hang out?
[cue falling in love and never meeting ex-wife.]
4. One scientist has the key to time travel.
Cut down on character actors and just have one crazy scientist who knows how to time travel or has figured out how it works. Also, make sure to obscure the fact that figuring out time travel would also finally connect quantum theory and the theory of relativity, and a legendary, Nobel Prize winning discovery that could change everything we know about the universe. The best version of this is when the main character has no idea how it works but he's the one who ends up going anyway. How's he even going to come back?
POC Scientist: Look, I made a time machine!
White Main Character: Let's go back to meet the Founding Fathers!
POCS: Nah, you go.
White Scientist: Look, I made a time machine!
POC Main Character: Let's go to the future and see what the world ends up being like!
WS: Nah, you go.
5. Stable time loops can be broken.
We totally create our own fate. Except we don't, because time travel ensures we don't go beyond the future that's been written for us, no matter how much the script gets twisted. It's a tricky piece of writing, but also very reliable.
Main Character: I'm going back in time to kill my enemy, who hates me for some unknown reason and won't leave me alone!
[goes back in time and finds burning car]
Person in Burning Car: Help me!
MC: Holy crap! [pulls person from the fire]
PIBC: Thank you for saving me!
MC: Obviously! What's your name?
PIBC: My name is [enemy's name].
MC: …why don't we just put you back in the car.
PIBC: How dare you!! Monster!! I swear revenge!!!!
At this point, you might be wondering why not just remake Back to the Future? That's the last rule of making time travel movies:
6. Don't try to remake Back to the Future.
Because chances are that if you tried, someone will come from the past and stop you.