Among files uncovered in the Gigaleak, a large-scale leak of assets from Nintendo's internal servers in 2020, are various assets from Super Mario World 2: Yoshi's Island depicting alternate ideas for Baby Mario. The earliest of these assets are a series of sprites from October 1993 depicting him in a bonnet and with a mustache similar to his adult counterpart; by comparison, the earliest sprites depicting his final design are dated to August 1994.

In the interim, however, Nintendo apparently considered omitting Baby Mario entirely; sprites dating to the spring of 1994 show that the developers considered having the Yoshi Clan ferry an infant wizard around instead. These sprites depict the wizard both in normal gameplay and in the pre-rendered CGI graphics used in the opening cutscene. Other sprites of the wizard show that they would've provided an in-universe reason for Yoshi's ability to transform into various vehicles: the wizard would cast a spell on a Yoshi egg while encasing themself and the real Yoshi in a bubble.

While the developers ultimately went back to using Baby Mario, the wizard still appears in a prototype build from December 6, 1994. In this iteration, the wizard is a form that Baby Mario can turn into through the use of an item depicting the projectiles fired by Kamek in the penultimate area of "6-8: King Bowser's Castle". This "Wizard Mario" form could similarly cast spells that transform certain enemies into objects such as eggs, watermelons, and Winged Clouds.