Some people have a sense for metalanguage, i.e. they think about language rather than just using it. A great example of that which trends toward the idea that you either have it or you don’t was found at McDonalds.
Only this McDonalds was in Moscow. A girl about 18 was behind the counter and when she asked what size I wanted, she said “large?” She used the feminine form but Pepsi ends in a vowel that gives no hint of gender. So I wondered why she said “bol’shaya” instead of either the neuter or masculine.
As busy as she was, I nevertheless asked her, “Why bol’shaya instead of bol’shoe or bol’shoy?” She took one second to think and then spouted, “Butylka”, which is ’bottle’ and is feminine. What insight! I loved it.