10 Horror Sequels That Totally Ruined The Previous Movie's Ending

10. I Still Know What You Did Last Summer

Based on the novel of the same name, 1997's I Know What You Did Last Summer follows four friends who accidentally strike a man with their car. Not wanting to get the authorities involved, they dump the body and vow never to speak of it again. When the hook-wielding Fisherman begins stalking the group the following year and taunts them for the hit-and-run, they realise they can't run away from their past sins.

The teen slasher made over $100 million on a modest budget, so it wasn't a surprise when a sequel was greenlit and arrived one year later. But there was a problem. 

I Know What You Did Last Summer concludes with our heroine, Julie James, returning to college after she seemingly killed the Fisherman. As she enters her dorm bathroom, Julie notices a message written on the mirror that reads "I STILL KNOW", and before she has a chance to react, the Fisherman bursts through the glass and attacks Julie, as the screen cuts to black.

Even though this was a great cliffhanger, a throwaway line in I Still Know What You Did Last Summer reveals that this incident was all just dream.

Though nobody should be expecting a Shakespearean level of writing from a slasher movie, using the "it was a dream" trope to explain away this moment was the first sign this sequel was going to be terrible.