火星弟弟
[huŏ xīng dì dì]
Refers affectionately and playfully to somebody akin to a Martian younger brother, implying differences from common earthlings due to their distinct personality traits - quirky, unconventional, alien-like demeanor, etc.; thus highlighting users' own characteristics in a fun light while embracing their uniqueness and individualism in society or communities where they belong culturally and ideologically.