沐猴衣冠 Monkey in fine clothes
Explanation
比喻外表装扮得体，而内心空虚，没有真才实学。常用作讽刺那些徒有其表，实际能力不足的人。
It is used to describe someone who appears decent and well-dressed on the outside, but is actually empty and lacks real talent or ability.
Origin Story
话说战国时期，楚国有个猴子，它特别喜欢模仿人的行为。有一天，它偷偷溜进了一个村庄，看到人们穿着漂亮衣服，便学着穿上。它笨拙地模仿人们的姿态，戴上帽子，穿上长袍，还真有几分像模像样。然而，它骨子里还是一只猴子，无论它怎么装扮，也掩盖不了它粗鲁野蛮的本性。这个故事后来被人们用来比喻那些外表光鲜亮丽，但内心空虚，没有真才实学的人，称之为“沐猴衣冠”。 后来，项羽和刘邦争夺天下，项羽虽然武力超群，却不懂得治国理政，最终败给刘邦。人们常说项羽“沐猴衣冠”，讽刺他虽然外表威风凛凛，其实不懂得如何治理国家，最终自取灭亡。
In the Warring States period of ancient China, there was a monkey that particularly liked to imitate human behavior. One day, it sneaked into a village and saw people in beautiful clothes. It learned to put them on. It clumsily imitated people's posture, put on a hat, put on a robe, and it really looked like a human. However, it was still a monkey at heart, and no matter how it dressed up, it could not hide its rude and barbaric nature. This story was later used by people to describe those who appear glamorous on the outside but are empty and lack real talent or ability, which is called "Mù hóu yī guàn". Later, Xiang Yu and Liu Bang fought for the world. Xiang Yu, although extremely strong, did not know how to govern, and eventually lost to Liu Bang. People often say Xiang Yu is "Mù hóu yī guàn" to satirize him that although he appeared majestic and imposing, he didn't understand how to govern the country, and ultimately destroyed himself.
Usage
用于形容人外表光鲜，但实际上才能平庸，缺乏实际能力。多用于贬义。
Used to describe someone who looks good on the outside but is actually mediocre and lacks real ability. Often used in a derogatory sense.
Examples
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他虽然穿戴华丽，但实际是个沐猴衣冠的家伙。
ta suīrán chuāndài huáli, dàn shíjì shì gè mù hóu yī guàn de jiāhuo.
Although he is dressed in fine clothes, he is actually a pretender.
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不要被他的外表所迷惑，他只是一个沐猴衣冠的骗子。
bùyào bèi tā de wàibiǎo suǒ míhuò, tā zhǐshì yīgè mù hóu yī guàn de piànzi。
Don't be fooled by his appearance, he is just a pretender in fine clothes..