In the book, it’s briefly mentioned that Williams felt threatened by Jim Carrey surging stardom, and apparently Williams became upset when he learned that Carrey had signed on to play The Riddler in 1995’s Batman Forever, a role that Williams had turned down.
This whole thing started when when New York Times journalist Dave Itzkoff’s new biography about Robin Williams, appropriately titled Robin, was released.
Williams’ makeup artist Cheri Minns confirmed that the actor did have some insecurity about Carrey’s popularity, recalling a time when Williams’ ex-wife Marsha told him that there was “room for other people.”