I am watching Supernatural!

Hi! So, im on episode 10 of season one, so far i am really enjoying the series, for example one of the things i really like is that the sidecharacters aren't completely unknowing as in other movies/series.

But okay that aside, what are some references or qoutes from the series that i won't understand until im at that episode or finished the wntire series. (I am sorry if anything here is written wrong or anything, english isn't my first language and also this is my first time posting on reddit.)