Two cartons of orange juice about to burst
It's the early 1960s. I am sitting on the floor in the living room of the house where I spent the first nine years of my life. But I'm not a child, I'm an adult: the person that is dreaming this dream. So how did I end up in the past, surrounded by my childhood toys? When I look around, I notice that my (adult) twin cousins are in the room as well. They have turned into statues, resembling the Anubis statues of ancient Egypt. In their stone-like hands, both cousins hold a carton of orange juice.
Puzzled, I approach one of them to have a look at the orange juice. When I get close, the carton becomes transparent, as does the orange juice. I can see thousands of small creatures swimming inside the carton. Roughly half of them are from our planet's prehistory; the other half is of alien origin.
The carton of my other cousin is similarly full of creatures, but they are different from the ones in the other carton. The two cartons are counterparts: male vs. female, positive vs. negative, hot vs. cold. If the counterparts interact, the creatures will escape into the wild. They will multiply rapidly, wrecking havoc on the environment and destabilizing the earth's ecosystem. This is something I have to prevent at all cost.
When I want to collect some stray toys from under the table, I disturb a creature that resembles a silverfish. Except that this one is about ten centimeters long, and capable of moving fast. It starts to run towards the cousin positioned near the window, and I know that when it reaches him before I do, both orange juice cartons will burst and trigger an ecological disaster.
Desperately I look for something to catch the creature with, but none of my old toys are suitable. I scream to my wife she has to come up with a solution, but then I discover she doesn't exist in this dream. So I start running after the creature that has the power to turn the earth into a prehistoric alien planet. It is already dangerously close to my cousin ...