Baymax is an Enlarging Skill Tsum Tsum. He also enlarges any Magic Bubbles. If any Bubbles are on screen for his skill, they take precedence getting enlarged over random Tsum Tsum. His base variation size is 2~3.
Popping enlarged Bubbles will count towards big Tsum Tsum missions.
Baymax could be used during the Japan Event Baymax (September 2019) and the International Event Save San Fransokyo! (April 2020) to clear missions more easily, because he had a character bonus.