Birdo as it appeared in Super Mario Bros. 2 (left) and Birdo in Mario Kart: Double Dash!! (right)

Birdo (Japanese: カサリン; Catherine) is a fictional, anthropomorphic dinosaur featured in Nintendo's Mario series of video games. While Nintendo has never made the exact nature of Birdo clear, it appears to be both a particular character and a species of enemy, just as Yoshi from Super Mario World can refer either to a class of video game dinosaurs or a particular one. Birdo first appeared in the Japanese game Doki Doki Panic as an end-of-the-level boss. Doki Doki Panic was later remade into Super Mario Bros. 2 for release in America.

Birdo is most frequently depicted as pink, though red and green Birdos are also seen in Super Mario Bros. 2 and other games. In Super Mario Bros. 2 Birdo was an end-of-level boss who would spit out eggs and/or fireballs from its tubular snout. After defeating Birdo by hitting it with the eggs or other nearby objects, a crystal ball would drop out from Birdo's belly, allowing the player to open up the gate to the next level.

Although later Nintendo mythology classifies Birdo as female, the first edition game manual described Birdo as follows: "He thinks he is a girl and he spits eggs from his mouth. He'd rather be called 'Birdetta." Based on this description, it is arguable that Birdo is the first transgendered video game character, but since Nintendo no longer refers to Birdo as a male, this is questionable. Further, Birdo is known in Japan as "Katherine". It may be that Birdo is asexual but identifies with the female gender of a culture; whether or not this counts as "transgender" would depend on one's views on Birdo reproduction and whether asexual would count as male, female, or a "third gender" when considering transgender issues. Similar issues exist with Yoshi.

Some confusion has arisen over Birdo because in the Super Mario Bros. 2 manual, Nintendo erroneously switched the images for Birdo and Ostro , an ostrich that playable characters can ride. Since then, many have confused the two.

List of other appearances

• In 1994, Birdo appeared in Wario's Woods on the NES in the Tutorial.
• In 1995, Birdo appeared in Super Mario RPG on the SNES as a huge boss encased in an egg.
• Birdo was a playable character in Mario Tennis for the Nintendo 64.
• In 2001, Birdo appeared in Super Smash Bros. Melee as a non-playable character in the "Mushroom Kingdom II" level. The image used in this game was the original image of Birdo from SMB2 to match the "retro" look of the level.
• In 2003, Birdo appeared in Mario Golf: Toadstool Tour as a playable character, Mario Kart: Double Dash!! on the GameCube as a driver with Yoshi, and in Mario & Luigi on the GBA as a character in love with Popple, a thief (an inter-species love interest).
• In 2004, multiple Birdos make cameo appearances in Mario Power Tennis in the audience. Multiple Birdos are seen in the audience, ranging from green to tan.