Why is Pikachu called Pikachu?
"'Pika' is the sound Japanese say an electric spark makes. And 'chu' is the sound a mouse makes."
-Satoshi Tajiri, creator of Pokémon
A mix of a Birdo and a Pikachu is called a Birdachu. It has it's normal Birdo body with Pikachu's tail, ears and cheeks. It's belly is yellow as well. In order to give birth to a Birdachu, you must have a female Birdo and a male Pikachu make a baby together. (With a Yoshachu, it's the other way around.)