The late, lamented Robin Williams got to tackle more than his share of memorable roles during his career, but we never got to see him play a villain in a Batman movie.

It wasn’t for a lack of willingness on his part. Williams wanted to play the Joker in the 1989 Batman film, a part that famously was portrayed by Jack Nicholson, and reportedly was in talks to play the Riddler in Batman Forever before Jim Carrey was ultimately cast. So why didn’t we see Williams ever face off against either Michael Keaton or Val Kilmer as the Dark Knight?

If you read Brian Cronin’s Comic Book Legends Revealed ongoing feature on the Comics Should Be Good blog — and you should, because it’s consistently excellent — you already know the answer, or at least as close as we’ll ever get. The circumstances were different in each case: for Batman, Cronin says Warner Bros. always wanted Nicholson as the Joker and simply used Williams’ known desire for the role as leverage in negotiations.

Williams was closer to featuring in Batman Forever, but his assertion in a 2010 interview with Empire and Cronin’s conclusion differ. Namely, Williams suggests that the Riddler part was offered to him and then taken away to give to Carrey, while Cronin’s research leads him to state that the actor walked away from the part because of unhappiness with the studio and the casting of Tommy Lee Jones as Two-Face.

Since Batman Forever was ultimately forgettable aside from Seal’s contribution to its soundtrack, Williams probably didn’t miss anything by dropping out, if that was indeed the case. I’m not 100 percent convinced the Riddler would have been the proper fit for his manic improvisational skills, as Carrey went in that direction with his characterization and it didn’t feel like the Riddler you’d expect.

But the Joker is a different story. As much as Nicholson made that part his own at the time, the thought of a Robin Williams Joker has to go down as one of the great “what ifs” in super hero movie history.