萌比小欧巴
[méng bĭ xiăo ōu bā]
In this case, '萌' (moe) refers to adorableness/cutie. And '欧巴'(op'a), originally a Korean word, is used by Chinese-speaking fans referring affectionately to older male K-pop stars or men in general they look up to. Therefore, this nickname describes someone considering themselves cute/adorable like a favorite idol star, showing their idol worshiping and fan-culture influence.