T minus zeroby
KaliComment by K3Master: When he had written the note on that piece of paper that day, and folded it into a plane, and went up to the top of the ridge over-looking the town, he had thought it a lark, a joke, good times. The chances of anyone finding it and responding to those silly words -- "Please help me, I am a pilot on a mission of great importance for the Paper People. I am going down, mayday, mayday." it read -- was very slim. Maybe it would get a note in the local paper, was the most his imaginative mind could conjure. More like, he would give someone a little chuckle before they balled it up and tossed it in the trash.
So were his thoughts when he stood there, and reared back, and tossed that plane into the emptiness before him, and watched it catch a breeze and float off out of sight. He smiled and rejoined his parents and continued on his hike.
Had he really known what would happen, perhaps he wouldn't have been so innocently foolish. Perhaps.
In a freak, million to one chance, that paper airplane hit a dimensional rift at just the right time, and ended up in the hands of an inter-dimensional protectionary unit. Not knowing Earth, or its peoples, it translated the note on the paper plane and took it seriously. Very seriously indeed.
Not long after, when the rifts began opening in the skies above our planet, and the ships started coming through, we were doomed. Sadly, they never did find the Paper People.