This is a way that you joke in American English that if the person were to know you that what they have said would not be true. Or that it is very true, depending on the context.
I hope that this helps :)
You may be someone important - or you may be a friend of a friend, or someone who knows another person through work. You can say jokingly, "Guess who I am?"
あなたは重要人物、友人の友人、仕事を通して知り合った人かもしれません。冗談交じりに以下のように言えるでしょう。
Guess who I am?
（私を誰だと思っているの？）
Native speakers will say like this: “You must've mistaken me for someone else!”.
There are lots of other ways to say it, but this one is the most accurate and most commonly used.
Here is an example on how to use this in a conversation:
A: You're beautiful and well mannered. I wish more people were like you.
B: Hah! You must've mistaken me for someone else!
ネイティブスピーカーは次のように言います。
“You must've mistaken me for someone else!”
(誰かと勘違いしてますよ、きっと！)
他にもいろいろな言い方ができますが、これが最も正確で一般的です。
以下、会話例です。
A: You're beautiful and well mannered. I wish more people were like you. (あなたは綺麗で上品です。あなたみたいな人がもっとたくさんいたらいいのに)
B: Hah! You must've mistaken me for someone else! (まあ！誰かと勘違いしてますよ、きっと！)
"Do you even know me?" is made a joke by the addition of the word 'even' in to the sentence and the way that the phrase is spoken, usually in a sarcastic manner.
"Have we met?" This phrase is best used when speaking to someone who you actually know very well. It is a straight alternative to saying "Who do you think I am?".
"Do you even know me?"
私を誰だかわかってる？
'even'を付け加えることで冗談ぽくなり、皮肉まじりに聞こえます。
"Have we met?"
会ったことあったっけ？
これは、自分のことをよく知っている人と話すときに使える表現です。「私のこと誰だと思っているの」という意味のストレートな表現です。
Both of these can be used in a joking way but it all depends on the tone of your voice or to add some sarcasm into it, it then gives it a different meaning in a more joking way
日本 
南アフリカ 
アメリカ合衆国 
イギリス 
カナダ 
