在他婚礼上唱小三你好贱
[zài tā hūn lĭ shàng chàng xiăo sān nĭ hăo jiàn]
This implies a rather sarcastic and derogatory situation where someone is singing at another's wedding while acknowledging themselves as the third party (a mistress). This net name can be understood as criticizing the unethical relationships.