How do u unlock the pink female Yoshi-looking thing on mariokart wii?

i've seen ppl using a pink character that loox like Yoshi/a kangaroo while playing online with the Nintendo Wii. She has a big red ribbon on her head. Here's the character: http://content.answers.com/main/content/wp/en/1/14/Birdo_nintendo.jpg

How the hell can u use this character? If i have 2 have another game 2 unlock her, is there a way around it like there is to unlock Rosalina? Cuz if u only have mario kart & not mario galaxy, u can still unlock a certain character [Rosalina, keeper of the stars] by getting a 1-star r8ng on each mnirror mode cups. Is there something like that that i'd have 2 do 2 unlock the female Yoshi thing?

Just an xtra thing, i also saw sum1 using a Scooby-Doo character on Mario Kart online [Wii]. How the hell do u get stuff like that??? Thanks!