Robin Williamswas one of the most beloved actors of his generation.
His fans were heartbroken to learn of his death by suicide in August 2014 (viaThe Hollywood Reporter).
Apparently, Williams reached out to the film’s director, Chris Columbus, about taking on the role.

All the main characters in “Harry Potter” had to be played by British actors.
The role of Hagrid, of course, went to actor Robbie Coltrane (perIMDb).
Coltrane would portray the character in all eight “Harry Potter” films over the following decade.
