Director Christopher Nolan spoke to Entertainment Weekly about Heath Ledger for this week's issue .

Here are highlights of what Nolan had to say about the man who plays The Joker in the The Dark Knight:

On Heath's commitment to his character: "The guy had serious nuts. What I needed was someone who wouldn't be afraid of the comparison with Jack Nicholson. And then I saw Heath's incredible performance in Brokeback Mountain. Such a lack of vanity. This was an actor who wasn't afraid to bury himself in his character â€" to a massive extent."

On Heath spending months working with a voice coach fine-tuning the Joker's cackling cadence: "He tried to articulate to me what he was doing with his voice, but it was sometimes hard to understand. He talked about ventriloquist dummies, the way their mouths moved, the way their voices wouldn't appear to come out of them. He said he wanted the voice to have a mocking quality, a sort of disconnectedness."

The viral marketing for The Dark Knight revealed this new poster today for the movie this week.

In the past week, movie critics and directors have absolutely gushed about the film. It opens on July 18.

Movie critics have already raved about The Dark Knight.

Director Kevin Smith (Clerks, Mallrats) just saw the film and he raved about it on his blog.

"Courtesy of Peter Sciretta over at SlashFilm.com, I caught an early screening of "The Dark Knight" yesterday evening.Without giving anything away, this is an epic film (and trust me: based on the sheer size and scope of the visuals and storytelling, that's not an overstatement).

It might not be humanly possible to look forward to a movie more than we're looking forward to The Dark Knight.

It's the "Godfather II" of comic book films and three times more earnest than "Batman Begins" (and f-ck, was that an earnest film). Easily the most adult comic book film ever made. Heath Ledger didn't so much give a performance as he disappeared completely into the role; I know I'm not the first to suggest this, but he'll likely get at least an Oscar nod (if not the win) for Best Supporting Actor.

F-cking flick's nearly three hours long and only leaves you wanting more (in a great way). I can't imagine anyone being disappointed by it. Nolan and crew have created something close to a masterpiece."

Warning: The Dark Knight spoilers ahead!

In a recent interview with MovieWeb, Gary Oldman - who plays Police Commissioner Gordon in the latest Batman franchise - praised the performance of Heath Ledger in The Dark Knight, while also giving away the ending of the movie to an extent.

"It's hard to scare kids these days. Heath does. He scares everybody," Oldman said. "This is one of the most frightening performances I have ever seen put on film."

When asked if he thought they should recast Ledger for the third film - giving away the fact the The Joker survives in The Dark Knight - or just not include the character, Oldman leaned toward the former.

"I don't see why not. I mean, they did it with Katie Holmes' character. I understand that this is a different circumstance, but I think another actor could do the job. I think Heath would want another actor to do the job."

Those that have seen Batman Forever are familiar with the Tommy Lee Jones-portrayed character of Two-Face. They're also familiar with the lucky coin he carries around.

With that in mind, take a look at the following image from The Dark Knight.

In it, Aaron Eckhart - who takes on Harvey Dent/Two-Face in the latest Batman movie - is shown fingering a certain round piece of metal:

If it were up to Peter Travers, a movie critic with Rolling Stone, Heath Ledger would be nominated for an Oscar for his role in The Dark Knight.

"I can only speak superlatives of Ledger, who is mad-crazy-blazing brilliant as the Joker," Travers writes in the movie's first published review.

The praise certainly doesn't stop there, as Travers goes on to say:

"It's typical of Ledger's total commitment to films as diverse as Brokeback Mountain and I'm Not There that he does nothing out of vanity or the need to be liked."

Might Heather Ledger earn an Oscar for his work in The Dark Knight?

Travers added that there's "no plastic mask for Ledger. His face is caked with moldy makeup that highlights the red scar of a grin, the grungy hair and the yellowing teeth of a hound fresh out of hell." He then makes his Academy Award pitch:

"If there's a movement to get him the first posthumous Oscar since Peter Finch won for 1976's Network, sign me up."

Earlier this week, Entertainment Tonight gave viewers a sneak peek at The Dark Knight.

Looks like a motorcycle crash gives The Joker a free shot at Batman in the clip. Take a look:

In this new television spot for The Dark Knight, we get a new glimpse of The Joker.

Beware, fans that don't want too much revealed: the following clip does show some pretty cool scenes.

In this quick clip from The Dark Knight, we get our first look (or listen, anyway) at Two-Face:

Here's the clearest picture yet The Joker from The Dark Knight.

As the world sadly knows, of course, this was the last role of Heath Ledger's career.

Meanwhile, here's the latest TV spot for the movie: