Insert DeVito’s penguin chuckle here. The character actor is well-known for playing a signature baddie, especially in 1992’s Batman Returns, alongside Michelle Pfeiffer’s Catwoman, along with his other iconic roles of Mr. Wormwood in Matilda and his longtime mischief as Frank on It’s Always Sunny In Philadelphia. He loved the idea of going back to playing a character of a softer, kind-hearted nature with Disney’s Dumbo, especially since Keaton would now be the one he gets to steal the good guy glory from.
Article source: https://www.cinemablend.com/news/2469311/danny-devito-teased-michael-keaton-about-dumbos-batman-returns-role-reversal