If you start to emulate the people you spend the most time with, it stands to reason you'd pick up their weird quirks also. AJ is convinced he only drools in his sleep now because his girlfriend does. McCall thinks AJ doesn't know that sleeping can be better because he only knows snoring. Everyone shares the weird quirk of having a hierarchy of things they'd save in a potential house fire? An engagement ring would probably be at the top of the list, right?