Here is a selection of writing prompts from Reddit. These were all found on r/WritingPrompts.

[WP] "To be honest, we don't know yet WHEN the movie is going to be set. Somehow the time machine we use has been turned to ‘random’ and no one knows how to change it back."
byu/AnselaJonla inWritingPrompts
[WP] You are getting ready for a date with your girlfriend when you hear a knock at the door. Unexpectedly you find your girlfriend, however she is in tears and is begging you not to go on your date with her tonight. She also appears to be years older than the last time you saw her.
byu/Arch_Magos_Remus inWritingPrompts
[WP] As you are escorted into Hell, you ask the Demon, "I don't understand–I went to Hell for killing someone so why do I get this much freedom?" Turns out the person you killed in self defense was at the top of Hell's 10 Most Wanted list and the demons are paying you back.
by inWritingPrompts
[WP] Your roommate comes up to you and says "Look, I've been covering your half of the rent for the past 7 months now and enough is enough. Either start covering your fair share or start looking for a new apartment." Problem is that you're a ghost and your roommate doesn't seem to realize that.
byu/Twisted_Self inWritingPrompts
[WP] Religious people across the world celebrate as it is proven humans were created by a designer. But now it's scientists job to discover which religion got it right…
byu/Working_Ad_9637 inWritingPrompts
[WP] Sentient life was supposed to have been impossible on Earth, as Earth was created as a prison for nightmarish beings and eldritch abominations. As such, the Galaxy was very surprised when humanity made contact, and even more surprised when they discovered that humanity was, on the whole, sane
byu/archtech88 inWritingPrompts
[WP] "Don't open the door!" she screamed at the TV. "Who said that?!" asked the character on screen as he turned and locked eyes with her.
byu/godlovesaliar inWritingPrompts
[WP] You accidentally destroyed the universe, and you were the only survivor. But not all is lost. A friendly interdimensional being introduced you to U-bay, so youcan get a second-hand universe to replace it. But what does "gently used" or "some wear and tear" even mean in this context?
byu/nobodysgeese inWritingPrompts

Visit r/WritingPrompts for more.