Robin Williams missed out on playing Remus Lupin.
On Thursday, director Chris Columbus revealed that the late star was interested in playing the werewolf who is first introduced in "Harry Potter and the Prisoner of Azkaban," the third book and film in the franchise.
According to Columbus, Williams lost out on the role because hiring him would have broken a rule to avoid casting any American actors in an attempt to "maintain a degree of authenticity."
"I had a conversation with Robin Williams, who wanted to play Lupin," Columbus told Total Film, as quoted by GamesRadar. "It was very difficult for me to say, ‘It’s all British. There’s nothing I can do.’"
Columbus, who directed both the first and second "Harry Potter" films, is American. Mexican film director Alfonso Cuarón took on the third film, which features Lupin, played by British actor David Thewlis. The 58-year-old played the role until his final appearance in 2011.
In 2016, casting director Janet Hirshenson told U.K.'s HuffPost that Williams was turned down for the role of Hagrid.
"Robin had called [Chris Columbus] because he really wanted to be in the movie, but it was a British-only edict, and once he said no to Robin, he wasn’t going to say yes to anybody else," she said at the time. "It couldn’t be."
That role was played by Scottish actor Robbie Coltrane.
Williams, who passed away in 2014 at age 63, told the New York Post in 2001 he lobbied for a role in the "Harry Potter" franchise.
"There were a couple of parts I would have wanted to play, but there was a ban on American actors," said the star, as quoted by U.K.’s Independent.
"Maybe one day," said Williams. "Say if [Harry] goes to Yale and becomes president."
The outlet noted that Williams attended the New York premiere of "Harry Potter and the Philosopher’s Stone."