Kingdom Hearts 3: 13 Ways To Include Every Pixar Movie
5. Cars
How: A summon.
Love it or hate it, the Cars franchise is staggeringly popular and financially lucrative even if it's frequently deemed "lesser" in comparison to Pixar's other series. As such, it almost seems a no-brainer for it to be included in the Kingdom Hearts series in some form, particularly as some sort of summon.
Having Sora and the gang take on car forms would undoubtedly limit combat, making a Cars world an intriguing but difficult sell, but it would make far more sense for the denizens of Radiator Springs to be called upon in battle. From Lightning McQueen turning up to speed around the field to Mater bumbling his way through defeating Heartless, being able to summon one or more characters would be an easy (and fitting) way to bring the franchise into the fold and capitalize on its popularity.