Ok, so obviously this is a pretty controversial call to make. With the passing of Heath Ledger, the question of having The Joker return for Batman 3 isn't just a frivolous argument about "what's best" for the movie - it's also a question of narrative relevance, audience reaction, and plain old-fashioned good taste.
As I said in our last Batman 3 feature, the question of whether or not you want The Joker brought back for B3 really depends on whether or not you think an actor is more important than the character they play or vice versa. However, this is THE JOKER we're talking about - the character is a genius creation of pulp fiction who has become a bonafide worldwide icon. There simply is no bigger villain out there right now and the character is going to endure long after the celebrations of Ledger's performance grow silent. And when those celebrations do grow silent - whether it happens next year, or another decade from now - some other talented actor is eventually going to step up and take a crack at the role.
More to the point, NOT having the Joker in Batman 3 would be a HUGE distraction for many viewers. The Joker is such a forceful presence that every second of him not being onscreen would be like an incurable itch in some folks' necks. People could literally end up sitting in theater going, "Oh here is where they had to write around The Joker," or "This where they COULD HAVE had The Joker if Ledger was alive. Bummer."
But let's drop all pretense: Really, Nolan and Co. will ultimately find themselves damned of they do, and damned if they don't. Not having the Joker would be a distraction for some, but having another actor step into the role would also force other viewers into the unfavorable position of having to watch the film picking apart how the new actor is different (read: not as awesome) as Heath was. It would be a lively debate, but I suspect not that fun of a viewing experience.
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The double-edged nature of this Joker dilemma makes a strong case for the assertion that Batman 3 should strike a narrative middle path of acknowledging The Joker, without engaging the character directly. Some have said the best way to do this would be to introduce the character of Harley Quinn (above), who could be a "disciple" of The Joker (totally embodying him in spirit), without the messiness of having to deal with The Crown Prince of Crime directly.
I myself have proposed one scenario which I could happily live with. It would be a cinematic nod to The Joker - much like Iron Man did with War Machine. Picture: You do a scene where a main character walks past The Joker's padded cell and all we see are his eyes, or maybe just his lipstick grin through a window. In the end, that main character keeps on his/her way, not yet ready - both literally and metaphorically - to "open that door" just yet. Cue a voice-over of Heath's nasally laugh... It's really the most honest, yet entertaining way to address this sticky situation, IMHO.
[WARNING: I'm about to say something that will likely turn you against me.]
However, something that has not yet been discussed at length is just what kind of purpose The Joker would serve in Batman 3. Unlike Two-Face (for the reasons stated on pg. 1), I totally believe that Nolan and Co. squeezed all the best juice out of the Joker/Batman relationship in The Dark Knight. I also believe that if The Joker were to return for the next sequel, the character would either have to play a diminished role (which The Joker almost never does), or we would end up basically getting re-hashed Dark Knight as the dramatic center of the movie. The last film was all about the chaos inspired by The Joker's reign; this next sequel has the task of dealing with what happens to Gotham City in the wake of that chaos - not what would happen if that chaos were unleashed all over again!
MY VOTE: It's hard to envision a Batman 3 scenario that would make proper use of The Joker. Then again, it IS The Joker we're talking about, and having the character around is almost always more fun than the alternative. In the end, I really can't call it: This Joker dilemma seems to be a mountain Batman 3 is just going to have to climb. And however the filmmakers choose to handle the issue, I can guarantee that SOMEBODY, SOMEWHERE, is going to feel cheated by the outcome. No wins in this situation.
Suddenly a fresh start is not sounding so bad... (See next page)