In Cells at Work!, bacteria and viruses are effectively presented as alien invaders.The Brave Fighter of Legend Da-Garn: One being launched against Earth is what causes it to select Seiji to awaken the Braves from their slumber.After the Big Bad was destroyed in the first season finale, the next two seasons had extradimensional aliens as their main villains. Today, similar themes are found in techno-thrillers, and crop up in works like Red Dawn (1984) and The Tomorrow Series, where similar feelings of dread at being dominated by a foreign and advanced enemy proliferate. Xenophobia would often play up the foreigness of said foreign empires with the aliens in The War Of The Worlds themselves being an allegory for imperialist powers invading and exploting supposedly "inferior people", the narrator noting that the Martian invasion wasn't so different from what Britain was doing around the world itself. It was actually a variation on another theme popular at the time, the " invasion story", where another country's army, usually France or Germany (depending on who relations were worse with at the time), would try to conquer Britain. This trope, in its modern form, was created by H. The Infiltration is especially popular as a metaphor for the Red Scare. Often an allegory for some Earth-based conflict, either one that's happened in the past or one that people fear may happen.