The effects can be anything from starting with nearly a level five hyper bar or invisibility, longer duration of X Factor and it goes on, and the cards feature many characters from both universes, many of which are not selectable characters in the game. (thevitalounge.net)
There are also a number of selectable character models, including several female variants. (thesixthaxis.com)
Well, if Diddy Kong Racing DS is any indicator, they only removed Conker the Squirrel and Banjo the Bear as selectable characters leaving the rest of the roster intact. (nintendoworldreport.com)