Transvestitism, transsexualism: that's all gravy.
But what I really love is when a guy knows that he should have been born a female (i.e. Transsexual); so he goes through hormone replacement therapy, which takes over a year, then has sex reassignment surgery.
So now (s)he identifies as a female and looks like a female and has all of the parts that a female has, but then, after living as a female for months, (s)he realizes that (s)he has made a huge mistake.
So (s)he goes through hormone replacement therapy again and has sex reassignment surgery again and becomes a male again. Then he is just really confused and goes to therapy.
I saw a special about this on Discovery Health channel.