你又不是塑料袋别装来装去
[nĭ yòu bù shì sù liào dài bié zhuāng lái zhuāng qù]
This nickname suggests that one should not pretend to be someone they're not. The phrase 'act like this and act like that' implies constantly putting on different appearances or personas in a disingenuous way. By comparing people who pretend to plastic bags used for packing, it carries the sarcasm of being overly pretentious.