The movie takes place in the Marvel UniverseThanos is testing out his Infinity Gauntlet or his Cosmic Cube, and causing the mass suicides to appease his mistress Death. It makes more sense than the plants being responsible.
The movie takes place in the DCUAnd the plants beeing sentient and developing the ability to evolve was all a plot by Poison Ivy. It wasnt the power of love that defeated the aliens The Goddamn Batman fixed the problem
The Crazy Old Lady was responsible.How much better the twist would have been if there was a scene where the old woman is ranting to the protagonists and she says "I don't like being around people, but plants? They've always been my friends. I'd rather talk to them than people. Sometimes I get so angry with people. That's why one time I just told my plant friends to just 'go ahead and kill everybody.' " She could be crazy, or she could have been responsible.
It was aliens!!They were actually the ones doing it, instead of plants as people had assumed. And it wasn't just certain people affected, in the area EVERYONE became controlled, but there were two phases. The strong willed were affected with 'phase one' and killed themselves. But 'phase two' showed no symptoms until finally the aliens become ready to strike. And we don't see when they start attacking their fellow humans with all the knowledge and skill they normally have at the will of the aliens who wish to take over earth.
Elliot was unable to find work as a schoolteacher due to the number of teenagers and children who committed suicideAt the end he’s seeing Jess onto her bus for the first day of school at a time when one would assume he would be getting ready for classes himself.
It was THE BEES!The bees didn't die off. They just went to their secret headquarters and planned their revenge on the humans.
This takes place somehow, somewhere in the WhoniverseIt makes no sense, but the bees go missing for a time in the Whoniverse as well.
The movie itself was an experiment trying to get the audience to commit suicideLife imitates art.
The majority of people died when everyone panicked and started fleeing the cities.Once people found out they were in areas where the happenings occurred, they started jumping into cars and hitting the road, and forget about traffic laws! The scene where people start fleeing the diner after the news report, for example. Not to mention all the people who freaked out when they saw people killing themselves. One imagines people running in front of cars, in a blind panic.
GLaDOS is behind all of this!She somehow hooked herself up to all the plants in the world and started flooding the earth with neurotoxin! Wild Mass Guess made about A Troll in Central Park, The Happening is the story of how the Audrey II plant eventually wiped out most of humanity as told by someone hundreds or possibly even thousands of years after said plant's species had eaten most of Earth's populace. When all of the man-eating plants finally either left or died out, the few remaining humans tried to explain what had happened to the next generation. During this retelling of events, they had somehow managed to get a lot of the details wrong, but everyone agreed that the plants were responsible for the deaths of so many.
This movie and the remake of The Wicker Man take place in the same Universe.The women on the island in the Nic Cage version of The Wicker Man are certain that their honey harvest suffered last year because of the lack of a proper sacrifice (or something, I wasn't paying attention). It was actually because of all the disappearing bees that Mark Wahlberg mentioned at the beginning of The Happening. The women on the island probably hadn't heard of either event, being isolated on their insular island, and Nic Cage was too busy tumbling into the depths of depression and punching out women to explain.