Doing It for the Art: Karl Urban is a fan of the comics and actually defied the director during the filming, refusing to film a scene where Dredd would have taken his helmet off and show his face (something that is widely considered Canon Defilement by fans).
Dueling Movies: Avoided, or at least the "dueling" part. Though released within months of The Raid: Redemption, which shares an similar plot, The Raid's small release prevented most of the world noticing, and as Dredd was in production for years before The Raid came out, it was largely shrugged off as a coincidence. It also probably didn't hurt that Dredd (in concept, at least) is already based on a long-running and well-known franchise that involves similar concepts and themes to begin with.
Executive Meddling: Pete Travis was fired in post-production over delivering a film with not enough action and Alex Garland took his place in reshoots. Travis was later rehired and he and Garland delivered the final cut together.
Fake American: Despite all of its problems, Mega City One is clearly an attractive destination for immigrants.
Dark Helmet is Dredd (the large size of Dredd's helmet has caused this joke to be used quite often).
"The Pantene Thug" for the Ma-Ma Clan thug who, despite his dirty appearance, shows off his luxurious long black hair during the scene he says Dredd "hasn't gone down" shortly before Incendiary mode is demonstrated.
Fandom Nod: There are nods to Official 2000AD message board members:
Commando Forces whose name appears on a news ticker.
Goaty whose name pops up as graffiti inside the Peach Tress building.
Joe Soap and his forum avatar on a flyover at the beginning chase scene.
MichaelVK on a surveillance drone credited as "Michael Vee-Kay"
Recursive Adaptation: Ma-Ma's origin story was published in the Judge Dredd Megazine when the film came out and a year later, a sequel series was published with another on the way.
Vindicated by Cable: The film failed to recoup its production budget in its theatrical run, however it sold very well on DVD, including an annual campaign (The Day of Dredd) to get as many people as possible to buy and/or stream a copy of the movie on a specific date to draw attention to its Cult Classic status and hopefully inspire the production of a sequel.
Duncan Jones (director of Moon and Source Code) was offered the film, but turned it down, not because he didn't like Garland's script (Jones said it was great), but because he had such a strong idea of what he wanted to do with a Dredd movie, that he felt he could not bring himself to take it on and not do it his way.
There were three treatments that Alex Garland wrote before settling for the present story. The first treatment - the Dark Judges treatment features the encounter between Dredd and a rival judge by the name of Judge Death. However, Garland abandoned it after a year's work and 16 drafts on the story admitting that he couldn't crack much on that storyline. The second treatment is related to the Dredd and Cursed Earth storyline but was abandoned for the similar reason. The third treatment was an adaptation of the pro-democracy terrorists attacking the judges storyline but Garland felt that story and his ideas towards it were too grandiose in nature but stated that treatment would have been the third part of a trilogy, if there would be one. The final script that he wrote was based one of the punchier short stories in the vein of cop movies e.g Training Day. John Wagner described the script as correcting the mistake in the Stallone-starred version that was being too sweeping.