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Who's your favourite Partner from the Paper Mario series? and yes Pixls count as partners.

I like Bow from paper mario the best out of all the games but second is Ms. Mowz who wuz an optional partner and the Yoshi that you got to name.
Mine was black and I named it Miyamoto

YOSHI! The first time, my yoshi was black. What determines the color of the yoshi?

Once you have the egg, and when you’re 11th on the chart, (Save) then go fight
the iron clefts. In the match, run away on turn 1.
Go back and see what colour your Yoshi is.
Reset and fight the iron clefts again and wait the amount of minutes
given(below) to change the colour.
Colour you have:
Green – wait 6 minutes then run away to get a red Yoshi
Red – 3 mins to get blue
Blue – 2 mins to get orange
Orange – 4 mins to get pink
Pink – 3 mins to get black
Black – 1 min to get white
White – 1 min to get green

So if you originally have a blue Yoshi, and you wanted a black, then wait 9
mins in the battle.
I owe this little time guide to DarthMarth on gamefaqs.com