臭味相投 birds of a feather
Explanation
形容彼此的思想作风、兴趣爱好等相同，很合得来（贬义）。
describes people with similar minds, interests, and preferences who get along well (usually derogatory).
Origin Story
话说唐朝，有两个读书人，一个叫张三，一个叫李四。张三好酒好色，李四贪财好赌，两人臭味相投，常常在一起吃喝玩乐，挥霍钱财。一次，两人路过一户人家，看到院子里晾晒着许多上好的丝绸，两人心生贪念，悄悄地潜入院子，偷走了丝绸。然而，他们的所作所为，终究还是败露了。被官府抓获后，两人一起受到了法律的制裁。张三和李四的故事，成为了后世人们茶余饭后的谈资，告诫世人，千万不要与坏人同流合污，否则就会身败名裂。
In the Tang Dynasty, there were two scholars, one named Zhang San and the other Li Si. Zhang San loved alcohol and women, while Li Si was greedy for money and loved gambling. The two were birds of a feather and often spent time together eating, drinking, and having fun, squandering their money. Once, when they passed by a house, they saw many high-quality silks drying in the courtyard. The two became greedy and sneaked into the courtyard to steal the silks. However, their actions were eventually discovered. After being apprehended by the authorities, both were prosecuted. The story of Zhang San and Li Si became a topic of conversation for posterity, warning people not to associate with villains, lest they end up in disgrace and ruin.
Usage
用于形容人与人之间思想作风、兴趣爱好等方面非常相似，彼此很合得来（多含贬义）。
Used to describe that two or more people are very similar in their thinking, attitudes, and interests, and they get along well (often derogatory).
Examples
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这两个家伙臭味相投，总是干些坏事。
zhe liang ge jiahu xiùwèi xiāngtóu, zǒngshì gàn xiē huài shì.
These two guys are birds of a feather, always doing bad things. They are of the same kind, always together
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他们臭味相投，走到哪里都形影不离
tāmen xiùwèi xiāngtóu, zǒudào nǎlǐ dōu xíngyǐngbùlí