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(Character A) meets (Character B) at the Area 51 raid. (Character B) freaks out because they work there (albeit not voluntarily, it was a family thing to work for the government), and pretends they’re an alien because they’re a pathological liar.
Fortunately(?), (Character A) is stupid and believes them, so now (Character B) has to keep up with the charade after (Character A) takes them home to rescue them from the facility.