A Joke a day keeps the doctor away! (20-01-13)

A friend of mine, Jude, once told me this joke way back. It essentially goes like this:
Two guys who have not seen each other before met and this conversation ensued:

1st guy: Hello John, you have really changed.
2nd guy (surprised): Do I know you?

1st guy: You were tall before, now you are short.
2nd guy (confused): What!

1st guy: You were dark before, now you are fair in complexion? 
2nd guy: You are mistaking me for someone else.

1st guy: O John, you were fat before, now you are slim.
2nd guy: For goodness sake, my name is Peter, not John.
1st guy: Oh… You have changed your name too.