 However, on August 9, 2018, it was announced the episode premiered in January 2019.The entire cast is confirmed to reprise their roles with the exception of Ferb who will instead be voiced by David Errigo, Jr. Before the crossover aired, a character from "Phineas and Ferb", Dr. Heinz Doofenshmirtz, cameoed at the end of the episode "Fungus Among Us"; following the crossover, the characters Doofenshmirtz, Perry the Platypus, Major Monogram and Carl joined the cast of "Milo Murphy's Law" in a recurring capacity.