Does anybody knows coloquial meaning of ネギの妖精?


I know that literally this is related to green onion/leek, but there is this
sentence: あ、ネギの妖精だ。 ~~This is in the end of description, how stupid was
someone's actions.~~ I could possibly translate it to something like: "What a
moron." telling from context. Thing is, I realy wonder what is exact meaning
of ネギの妖精 and more generally, what is this in the first place? Thanks in
advance for your help!

Edit: Unfortunately, I had this context wrong - this sentence was used when
character had noticed that someone else started to removing the onion/leek
from her meal, because she was "not in the mood" to eat that kind of
vegetable. This was explained later, after this problematic sentence, but I've
stopped translating after being stuck on it. Nevertheless, with explained
context, the question is still valid.




I assume you think whole ネギの妖精 is a set phrase, but it's not.  
However, ～の妖精 is literally translated into "a fairy of ～," and is a funny
expression of "someone obsessed with ～" or "someone always attracted to ～" ,
which is sometimes used in gag manga.  
ネギ means a leek, so ネギの妖精 is someone {obsessed with/always attracted to}
leeks.  
More detailed context is required for better explanation, but "あ、ネギの妖精だ。"
seems a line in gag manga and the meaning you guessed was "What a moron," so
this meaning would be appropriate.

* * *

～の妖精 example:

A「キリマンジャロとブルーマウンテンの違いってわかんないんだよな」  
B「何の話～？」  
A「うわコーヒーの妖精が来た」

A: I don't know difference between Kilimanjaro coffee and Blue Mountain
coffee.  
B: What are you talking~?  
A: Aw a fairy of the coffee has come.

