In grammar class, the teacher asked a student a question, “Carlos, can you name two pronouns?” 

Carlos, who suddenly woke up, said, “Who, me?”

What's So Funny?

The teacher asks a grammar question to a student who was sleeping.  The student wakes up and is not sure of what is going on.  

What's a Pronoun?

Pronouns are a grammatical category of words that can substitute for nouns. For example:

• TEACHER can be substituted with SHE
• CARLOS can be substituted with HE
• THE PERSON BEING ASKED ABOUT can be substituted with WHO
• THE PERSON IN MY PLACE can be substituted with I or ME
• THE PERSON IN YOUR PLACE can be substituted with YOU
• THE PERSON IN OUR PLACE can be substituted with US
• THE PERSON IN THEIR PLACE can be substituted with THEY or THEM
• THE THING BEING ASKED ABOUT can be substituted with WHICH or WHAT

In asking if he is the person being called on, Carlos accidentally gives a correct answer to the teacher's question.  WHO is a (relative) pronoun, and ME is a (personal) pronoun.  Lucky Carlos!