한국말로 Something has changed이 뭐예요?
I am trying to find a way to say, "Something changed while I was sleeping," but there are so many ways to say "something" and "to change" in Korean that I can't find what I need.

In this sentence, "something" is not an actual thing. It's more like a feeling. Like if you look at a person and say, " Something about him is different."Here is my attempt:

자는 동안에 아무것이 변했어.ㅋㅋㅋㅋ "아무것이" 털렸어요. 미안해요.

Question

한국말로 Something has changed이 뭐예요?
I am trying to find a way to say, "Something changed while I was sleeping,"  but there are so many ways to say "something" and "to change" in Korean that I can't find what I need.

In this sentence, "something" is not an actual thing. It's more like a feeling. Like if you look at a person and say, " Something about him is different."Here is my attempt:

자는 동안에 아무것이 변했어.ㅋㅋㅋㅋ "아무것이" 털렸어요. 미안해요.

Answer

"Something has changed while I was sleeping" => 자는 동안에 무언가(가) 변했어 / 무엇인가 달라졌어.

아무것 is "anything", as in 뭐 먹고 싶어? / 아무거나 줘요 (Give me anything).

A simple rule is: something: 무엇, anything: 아무것, everything: 모든 것, nothing: (no matching word - 아무것도..아닌..).

무엇 means "what" in questions, and "something" otherwise.
When emphasizing the "unknown" nature, the "~인가" suffix is often added(무엇인가, 어딘가, 어디선가, 누군가).

So there are a few variations centered around 무엇 (what; something).
- 무엇인가 -> 무언가 -> 뭔가: emphasizes it is not definable.
- 무엇인지 -> 무언지 -> 뭔지: (similar)
- 그 무언가: "that something" - another way to emphasize it.

Here's an example usage of 무언가 (from a song):
- 어딘가 있을 무언가를 아직 찾고 있다 했지.
=> I said I was still searching for that something (that must be) somewhere.

Answer

"아무것이" 털렸어요 -> '아무것이'가 틀렸어요.   털리다 is a passive of 털다(dust; shake off / rob someone of money, valuables, etc), unrelated to 틀리다 (be wrong).