What I liked: Cory's humor column, Shawn's "Is it just me, or should that not make you happy?" line, Shawn as a girl, Shawn punching that guy, and saying it was for every girl he has ever known, Cory's "I decided to be a girl" line to his dad, amongst other things.
The only weak point for me would be Eric's plot with Lonnie, which did not interest me a lot, but that was only a small portion of the episode. The main plot had a good, original plot, and it was very funny. Definitely a classic episode, I would say so anyway. Grade would have to be an A+.