东施效颦 dōng shī xiào pín - Just a copy cat.
Make sure you understand the situation before you copy it.
If you don't understand what is really going on, you might end up looking like a fool.
The story takes place during the Spring and Autumn Period in Chinese history. There was a famously beautiful woman named Xishi (西施). She was beautiful but she didn't have a strong heart. She often suffered from pains in her chest where she would be forced to bend over and her face would cringe with pain. There was a girl in the same village named Dongshi (东施). Dongshi was not an attractive girl and grew quite jealous of Xishi. She wanted to know why everyone loved and adored Xishi so much. So she decided to follow her and imitate her actions. Dongshi saw that when Xishi bent over with pain and furrowed her brows she was quite lovely and drew the attention of all the men in the village.
So Dongshi decided she would imitate Xishi's actions to get similar attention. So she furrowed her brows and stooped over to look more like Xishi. However these actions only made Dongshi more ugly and repulsive and she did not get the attention she craved.
From this story we can see that without understanding the whole situation you may imitate an action that has the opposite effect of what you desire.
This phrase is still used a fair bit when someone copies someone else's actions and looks ridiculous. Here are some examples I found:
okay i just wanted to add a cat picture.
This phrase would probably also work for any "Nailed It" costume list.
Until next time, make sure you know what you are imitating!