Getting Back to The Keaton era of Batman , Robin was a character who seemed to be passed up until Batman Forever's production, When Keaton left .
Marlon Wayans and Ricky Addison Reed were actually cast as Robin during the Keaton era , but never made it to film.
O'Donnell was cast as Robin ,to be ,presumably opposite Keaton, but when Keaton left , O'Donnell acted against the younger Val Kilmer.
However, as a kid, I always looked forward to seeing how Michael Keaton's Batman would have acted with a younger Robin .
In the 1989-1992 period, there were several young actors I think who would have been great playing off of the then 40 something Keaton.
My guess is that Robin would have been , in all likelihood , Dick Grayson, though they probably would have incorporated elements of other Robins ,and characterize him in a way that distinguished him from The Burt Ward , " Golly Gee" Robin.
River Phoenix ( Stand By Me, The Explores , Sneakers)
I think the late actor, who was one of the best of his generation, would have made a great Dick Grayson slash Jason Todd style Robin .
He could also be charming as well, and I would have loved to see him act with Michael Keaton.
Wil Wheaton ( Stand By Me, Star Trek : The Next Generation)
If they were going for more of a contrast to Keaton, Wil Wheaton would have certainly fit the bill as a more light hearted contrast to Keaton's version.
His boy next door image may not have fit Burton's Batman world, but he would certainly fit the boy wonder image of Robin.
Sean Astin ( The Goonies, Rudy, The Lord Of The Rings Trilogy)
Like Wil Wheaton, he would probably fit into the more wholesome , light hearted ,Robin in contrast to Keaton .
He was another solid young actor who I think could have pulled off an earnest and naive Robin , being a rare light in Keaton's Bruce's life .
Ethan Hawke ( Dead Poets Society, Reality Bites)
Ethan Hawke would be more of an outside the box choice given his more dramatic filmography .
Then again, Keaton wasn't on anyone's bingo card when he was cast .
Hawke's roles , even as a youth, tended to be of young men more on the intellectual and idealistic side as opposed to alot of the normal teen heartthrobs of the 80s and 90s .
So , it would have been interesting to perhaps see a more cerebral Robin standing side by side with Keaton.
Christian Slater ( Robin Hood Prince Of Thieves , Young Guns 2 , Heathers)
The always entertaining Slater could certainly have played the wisecracking Robin in contrast to the more stoic and off beat Keaton Batman/ Bruce Wayne .
At the same time, as in Robin Hood Prince Of Thieves, he was also capable of playing dramatic and angsty as well , so , he could have played a more vengeful Robin , if that's the direction they wanted to go.
Michael J Fox ( Back To The Future, Family Ties , Teen Wolf)
During my childhood post Batman 89, he was the number choice of mine and of kids at my elementary school , even though he already would have been far too old to play Keaton's ward ,even by 1989, let alone 1992
.
Still, he would have made an interesting contrast to Keaton had Keaton started playing Batman in the early to mid 1980s .
