Room 203

Big Eyes, Baby, Yeongsam, Wang Nun...

Room 203 is a sadistic and mysterious character. He is known for his eery appearance and whimsically-murderous nature.
In Hell is Other People, the he is described by other character's as looking like an alien, and having a scary face.
I'm very fond of this character. I find his cartoonishly-evil manner and pointless sadism to be charming in a slasher movie kind of way.

Pointless Violence

The idea of humans being inheretlly evil is a reacuring theme throughout the trilogy, especially in Hell is Other People. This is attributed as coming from a Chinese Confucian philosipher Xunzi (episode 5.) Personally, I enterpret that room 203 is an expression of this idea being literal and true.
To me, this character kind of makes fun of this idea. Because he really seems to be pure evil, it creates contrast for the other characters in the story.

Absolutely the Worst Gay and Neurodivergent Representation

Another thing that this little goofball is known for is his apparent preference for men. He's appears to develop an infatuation with several men; Kang, Shim Gyu-heon, Park Minho, and finally, Yoon Jongwoo.
Wether or not he actually experiences any actual romantic and/or sexual attraction for these men is unclear. That being said, he sure uses some uncomfortably familiar language with them.