The best gender swap anime series of all time is Ranma 1/2. This Japanese anime series was made by Rumiko Takahashi (a female writer and illustrator) and ran from 1987 to 1996. The story is about a teenage boy named Ranma Saotome who went to China to train in martial arts and was cursed to become a teenage girl everytime he was splashed with cold water. He or she would have to bath in hot water to change back to a boy. This gender changing series is hilarious and very original.
In this irreverent but fun anime comedy, since he turns from a black haired martial artist into a cute red headed girl, there are lots of unwanted attentions from other boys. Ranma’s father was also cursed in China but he would change into a Panda instead. The lead female character is Akane and her relationship with Ranma is confusing and complicated because she knows about Ranma being cursed and would get weirdly jealous of his other half being a girl. More and more funny characters are introduced throughout the series and the plot thickens every time. This is not only the best gender bending anime, it is one of the best anime series of all time.