Mario Kart 8 Deluxe update adds 5 more extra character slots beyond Birdo

It would appear that Nintendo will include six new characters into Mario Kart 8 Deluxe

Mario Kart 8 Deluxe Booster Course Pass Wave 4 Review (Switch eShop)

Mario Kart 8 Deluxe – Booster Course Pass, ST, Doubled Dash!! [WAVE 6 AVAILABLE NOW], Page 137

My predictions of the likelihood each character has to return in the next mainline Mario Kart game : r/mariokart

On a scale of 1-10, how much would you rate the DLC characters we got for Mario Kart 8 Deluxe? : r/mariokart

Mario Kart Tour (Video Game) - TV Tropes

Characters - Mario Kart 8 Guide - IGN, mario characters

amiibo (Toys) - TV Tropes

On a scale of 1-10, how much would you rate the DLC characters we got for Mario Kart 8 Deluxe? : r/mariokart

Birdo's in! But who else will join?! Mario Kart 8 Deluxe Character DLC Discussion!

Mario Kart 8 Booster Course Pass: Yoshi Island and Birdo being added as DLC, Page 2

The Retrogaming Times - Thirty-Ninth Issue - July 2022

Why doesn't 'Mario Kart 8 Deluxe' have Birdo as a playable character? - Quora

King Dedede, Kirby Wiki