Gender transformations in Anime shows

[TGManiac]

I have a huge list of gender transformation anime series. And I was just wondering if anybody knew of any gender transformations in any anime series out? Like there could be one episode in an anime series where a anime character transformed into the opposite sex. Or there could be a series dedicated to a gender bender transformation all the time. So please if anybody knows of any anime series that has at least one gender transformation episode in it please let me know it would be a big help thank you.