#97 - Chicken Mario

There's concept art of an unused Chicken Suit for New Super Mario Bros Wii. While its function and purpose are unknown, it's known that it was later replaced by the Penguin Suit. A similar chicken suit appears in Volume 44 of the Super Mario Kun manga.

SOURCE: https://www.mariowiki.com/List_of_New_Super_Mario_Bros._Wii_pre-release_and_unused_content#Unused_Power-up