Let's see if we can amass 1001 ways the world might end. (dedicated to oinquarki)

#1. A collision with an asteroid.

#2. A large-scale infectious pandemic.

#3. Large-scale loss of fertility.

#4. A bomb kills everyone

#5. The Death Star turns out to be real.

-A black monolith appears in a colony of squirrels.

-All the zombies die.

self-replicating nanobots run amok,and we are buried in a grey goo.

Vogons. (be sure to count this as two.)

Psychlos invade earth and, with the help of John Travolta, enslave and then destroy all of humanity after taking away all our gold.

The Kraken is released. Again.

some kinda planetary orbit imbalance resulting in collision with Mars / Moon

Misuse of nuclear power resulting in a mass extinction event.

Sun will become a red giant and gobble up our Earth - this is the most likely thing to happen but we don't have to worry as that's gonna take another 5 billion years.

Misuse of coal power resulting in a mass extinction event...

We get hit by a GRB (gamma ray burster) star.

Super Massive Black Hole devoures the galaxy, but finds Dragons indigestible. >:[

-Confederate Nazis discover Greenland, carrying with them Odin's curse which contaminates all the pastries.

This world turns out to be a dream, and the person dreaming it wakes up.

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+1