Professor Robert Callaghan (also known by his alias Yokai) is the main antagonist of the Disney's animated feature film Big Hero 6. An aspiring man and world-renowed scientist, Callaghan's knowledge led him as a head teacher of the San Fransokyo Institute of Technology, though his true passion remained within his daughter Abigail, who was a tech pilot of Alistair Krei's industries. When his daughter became lost in a newly created portal, which served as one of Krei's latest projects, Callaghan descended to madness and vengeance, leading him to the birth of Yokai, a silent kabuki-masked super-villain with the power and numbers of Micro-Bots at his disposal. Ever since then, Callaghan attacked his former colleagues and prodigies, only to be finally stopped by Tadashi's younger brother, Hiro, whom he admired the most among his pupils.
While initially scheduled to appeared in the third installment of the cancelled Disney Villains War, Callaghan makes his full appearance in the second Disney Heroes vs. Villains in a role similiar to the original film, though this time revealing he is conspirator within the league of villains headed by Syndrome, Maleficent and Pete.