No one knew exactly where they came from. Earth visits by exoplanet aliens were becoming so common that the whole thing was humdrum. There were millions of different types of aliens visiting from all over the cosmos; so many that Earth decided to set up some sort of registration office. Each “species” of alien could await their turn. After all, they were basically “coming just for a look”. Like Earthling tourists in the old days, nothing was added to the Grand Canyon simply by having lots of inquisitive tourists. It would be different if an alien species came to share its technology with Earth.
Most exoplanet species didn’t mind the registration and visiting timetable schedule. A few exoplanet species however had evolved as deviants. Like the Earthling Communist Chinese of a previous era they had stolen the technology (in this case from other planets) – which was how they had the wherewithal to travel to Earth. Basically, when it came to being scientifically practical, they were relatively thick.
An example would be when they tried to bypass the registration setup. Some dumb exoplanet genius had devised a plan to infiltrate Earth by having a whole army pose as Earthling mailboxes. They were to stand motionless at every house gate and observe. (It must be added here for those who scoff, that these particular aliens were masters of transmogrification). They had missioned to Earth a team to capture the template of the basic mailbox. Moulds were made of the prototype. Thousands of mailboxes were manufactured. Each mailbox was imbued with the being of an exo-alien. The possessed mail boxes were placed at every earthling’s gate, replacing the mailboxes that were there.
There stood the aliens, motionless and observant; “spying” would be a better word. That was until Mrs Bridie McDonald of Chattanooga went out to check her mail. She was the first in the world that day to do so. She discovered that her mailbox no longer had any moving parts. They had ended up doing what the Japanese had done in an earlier Earth era: the Japanese had made trumpets with a mould so that there were no moving valves.
Every infiltrating mailbox was thrown onto a non-carbon-producing bonfire, and the dumb invasive exoplanet species were banned permanently from Earth. Way to go, Earthlings! Although, as an addendum, Mrs Bridie McDonald of Chattanooga did in later years admit to having found her mailbox particularly attractive – which might well explain why later that year her son was born with no moving parts.