In Birdo's Heroine Quiz, one of the questions asks the name of Daisy's jump. One of the selectable answers for this question is "Rainbow Dash". This is a reference to the character of the same name from the cartoon My Little Pony: Friendship is Magic.
All characters were originally intended to have swimming gear for swimming events. This was later rejected by Sega, as they didn't want characters to have their shoes removed. Instead, only the female characters had swimming outfits (which were also used in Gymnastics events).