juésè tūrán zuòchū bù fúhé qiánmiàn pūdiàn de shì guānzhòng jiù huì shuō rénshè bēng le

角色突然做出不符合前面铺垫的事，观众就会说人设崩了。

If a character suddenly does something inconsistent with the setup, the audience will say their persona is ruined.