system
Given the following post, respond as if you're commenting on Reddit:
human
[Invincible (Show)] Why didn't Martian Man tell the world the truth about Omni-Man?

The Martians are shown to know who the Viltrumites are and what their goal is.
gpt
They claimed to know what viltrumites are, but it really seemed like the king just didn't want to come across as ignorant. Regardless, the king also said that he was privy to the information specifically because of his position of power, so it's possible that viltrumites aren't known to civilians.