会发光是电灯泡
[huì fā guāng shì diàn dēng pào]
A literal translation would be 'If it glows, then it's a light bulb,' implying the recognition and acceptance of being a third wheel in someone's relationship or a group. In Chinese culture, the word 'light bulb' has become a humorous slang used for a person awkwardly intruding in couples' moments or when two persons want intimate time alone.