Brad Winderbaum, the newly promoted head of streaming, television and animation, talks the potential of live-action crossover: "It was a completely different muscle we were flexing."
For now, What If …? is focusing on characters who have already appeared in live-action. But animation history has noteworthy examples of popular characters who appeared in animation first before making it big in live-action. Harley Quinn debuted in the 1990s Batman animated series decades before debuting in Suicide Squad, while Ahsoka Tano, the fan-favorite Jedi, appeared in animation in 2008 before Rosario Dawson made the jump to live action in The Mandalorian season two. Now, Dawson is leading a live-action Ahsoka spinoff for Disney+, with sources saying Lucasfilm is looking for an actress to star opposite Dawson as Mandalorian warrior Sabine Wren.
It's long been rumored that the Ahsoka series will be a sequel to Rebels, picking up where that series ended 5 years after ROTJ (Ahsoka's episode in Mando is set BEFORE the ending of Rebels) with live-action Ezra and Thrawn, and this seems to be pointing to that if they're doing Sabine as well. They also just showed Hera's origin in Bad Batch.