不是只有超人才穿内裤在外
[bù shì zhĭ yŏu chāo rén cái chuān nèi kù zài wài]
Not Only Supermen Wear Underwear Outside: It's a playful reference indicating that one should not stereotype behaviors or appearances unique to superheroes like Superman who wears his underwear outside his pants. It reflects non-conventionality and humor.