Per Wikipedia:
Since the character's North American introduction, Birdo's gender has been an issue of discussion and speculation. The Japanese manual states the character's name is "Catherine", but it would rather be known as "Cassie." However, in the first edition manual for the North American release of Super Mario Bros. 2, Birdo is referred to as a male who believes he is female and would rather be called "Birdetta". In later printings, the second sentence was omitted, and no mention of Birdo being male was included in most later games featuring the character. In the Japanese version of Super Smash Bros. Melee, Birdo, called Catherine, is described similarly to the original manual, though wanting to be called "Cathy".[citation needed] In Super Smash Bros. Brawl, it is said that Birdo is of "indeterminate gender".[citation needed] Birdo appears in the Wii Japan-only video game Captain Rainbow, which delves into Birdo's gender. Birdo is often lauded as the first transgender video game character. The character was given a female voice actor in Super Mario Advance, a remake of Super Mario Bros. 2. The Spanish language website for Mario Smash Football, while describing Birdo, suggests that the character's gender is indeterminate. The European website for Mario Strikers Charged Football refers to her as a male character.
...and...
Birdo has been the subject of discussion relating to her gender issues. Gamasutra editor Simon Carless described Birdo as "infamously gender-confused." Birdo was praised by transsexual video game designer Jennifer Reitz. It is speculated by Wired editor Chris Kohler that the gender issue was retconned to make her female, while Reitz suggests that she received a sex change operation. In the book Vintage Games: An Insider Look at the History of Grand Theft Auto, Super Mario, and the Most Influential Games of All Time, the authors describe Birdo as the most notable character in Super Mario Bros. 2 due to being the first transsexual character in video games. GamesRadar editor Chris Antista has discussed Birdo in several articles. He listed Birdo #1. in his top seven "That's a Dude?!" game characters. He cited her bow, mascara, her being pink, and her being able to lay eggs as the identifying features of Birdo being female, while using the manual insert as the sole evidence to her being male. In the article "10 things you didn't know about Super Mario Bros 2," Antista listed Birdo's gender confusion, stating that the revelation was similar to when "lead singer of Judas Priest came out to a legion homophobic metalheads dressed to the nines in skin tight leather left wondering if their dicks will fall off." He also picked her as his first gaming crush, commenting that he worried that he would be outed once he read about her gender confusion in the manual.
In his article "Too Gay for the U.S.A.," editor Andrew Webster used the history of Birdo in the lead-in to his article, commenting on how Nintendo tried to hide Birdo's gender confusion, and how "He's just one of a long line of Japanese videogame characters forced to hide their true sexual identity". GamesRadar UK listed Birdo as one of "gaming's most repelling anti-babes," describing her as a "pink, egg blowing, transvestite dinosaur with a mouth like a burst fire hose," thereby describing her as "terrifying." Morgan Webb of X-Play created a video titled "Birdo WTF", commenting that everyone initially thought of Birdo as a "cute little dinosaur". He also describes her as a very feminine male character if she really is a transsexual. Nintendo Power listed Birdo as one of three weirdos, citing her change from being male to being a love interest for Yoshi. They described her gender as one of life's biggest questions, commenting on how she shoots eggs out of her mouth as another oddity. IGN editor Lucas M. Thomas commented in his article about Yoshi that Birdo "almost worthy of a whole other article," stating that she is "the most gender-confused character in the history of Nintendo." He commented on the relationship Yoshi and Birdo formed in Mario Tennis, stating that "Yoshi is supposedly a male, but lays eggs like a female. Birdo is supposedly a female, but was originally called a male. And now the two of them are a romantic couple? They were both sexually chaotic as individuals -- this new pairing just made your head hurt thinking about it."
