In an interview on Late Night with Jimmy Fallon (2009), Ben Affleck said he was warned by Warner Bros. about the possible negative reaction to his casting, and was advised to remain off the Internet after the casting announcement. He also said, to assuage his concerns, the studio showed him negative comments that fans had initially made to previous superhero castings. Affleck said in spite of the studio warnings, he still checked out an online message board. The first comment he read was, "Affleck as Batman? NOOOOOOOOO!!!!!!!!!!!" After seeing that, he immediately went offline.

In this film, Batman wears a voice modulator in his suit to electronically alter his voice. After the casting of Ben Affleck in the role, this was an idea that had been suggested by his friend, director Kevin Smith, as he felt Affleck's natural speaking voice was too high-pitched for Batman. He also felt it wouldn't sound like Christian Bale's voice in the Christopher Nolan Dark Knight trilogy.

In response to the negative and mixed reviews, Ben Affleck (Batman) said "We made this movie for the fans, not the critics." His co-star Henry Cavill (Superman) said similar things in other interviews.

Ben Affleck gained an additional twenty pounds of muscle and reached eight percent body fat for his role as Bruce Wayne a.k.a. Batman.

According to Ben Affleck, he was surprised when he was offered the Batman role, and was at first hesitant to commit to it. He was won over after a meeting with Zack Snyder, who pitched Affleck his vision of Batman, and showed him concept art for the film.

Continuity

When Perry reads the newspaper, an article refers to the African incident as having taken place in the real-life city of Nairobi, even though the incident in the movie happened in the fictional country of Nairomi.

When Diana is checking the email sent by Bruce, the total size of the attachment displayed at the bottom of the mail is 24 MB. Yet, the total size of each file when she open it is almost 800 MB.

Superman gets his hair messed up during his fight with Batman, but while he is fighting Doomsday his hair is perfectly combed again.

During the chase scene the Batmobile is right behind a lorry but there is no sign of it as Batman turns the corner & sees Superman.

The kryptonite spear "powers down" after Batman tosses it then Lois drops it into the pool, yet "powers up" when Superman retrieves it.



Factual errors

In the footage of Cyborg watched by Diana, the time is given as "2400 hours and 2 minutes." This is not how a 24-hour clock would keep time. It would be "Zero hours and 2 minutes."

At the start Bruce Wayne runs into a massive dust cloud formed from the falling building. In the scenes that follow he and the other people have very little or no dust on them at all - they should be completely covered and choking on it.

The Earth is constantly moving. Even if Doomsday and Superman were in space for only a few minutes after the nuclear explosion, the Earth below them would have rotated dozens of miles past their launching point meaning that returning to Metropolis would have had to been an intentional act of flying and navigation. In Doomsday's case, the film does not demonstrate this.

When Bruce Wayne watches the video footage of meta humans, the one with Diana takes place in Paris, France. The footage shows a date in the upper left corner. The date says "22 juin 2015, 10:13AM". If "22 juin 2015" is French, "10:13AM" is pure English. In French, the hour would simply be "10:13" (as the evening time would be "22:13").

Courts of Appeal do not call witnesses. Therefore, Lex would not have won his appeal because Superman was unavailable to appear as a witness. Superman Returns (2006) made the exact same mistake.



Incorrectly regarded as goofs

When Superman and Batman are fighting, Batman releases a smoke bomb. Superman could use his X-ray vision to follow Batman's movements, but he looks surprised when he goes through the smoke and Batman is gone. In fact, these bombs contain lead which disrupts Superman's vision. When Batman is preparing his bombs in the Batcave, a chemical formula is written on each bomb, the letters "Pb" are present (symbol of lead).

The four-inch cut in Superman's cheek from the Kryptonite knife disappears in subsequent scenes, leaving not even a scar. But this is because the cut healed itself when Superman is in space and gets revitalized by sunlight.

When Batman goes to save Martha Kent and breaks into the last room where the guy is holding the flame thrower on Martha he grabs the machine gun out of one of the henchman's hands. The machine gun is an M-60 which is a belt fed weapon but there's no belt on it so the weapon is unloaded. Actually if observed closely, attached to the side of the M-60 is a small box magazine that has bullets being fed by a belt into it showing that the weapon is indeed loaded.

Lieutenant General Calvin Swanwick became Secretary of Defense only 18 months after the events of Man of Steel, the previous film in the series. Without Congressional waiver, retired military personnel are prohibited from assuming the role of Secretary of Defense for a minimum of 7 years after retirement due to the National Security Act of 1947. Though rare, such a waiver has been granted twice, in 1950 for Secretary George Marshall, and again in 2017 for Secretary Jim Mattis.

When Batman removes his mask in the cave after the Batmobile chase, his eye make-up is gone. Similarly after Superman removes Batman's mask in the Knightmare scene the eye make-up is also not present. However, eye make-up has always been used to make Batman's eyes look dark in film adaptations since Batman (1989) to make the costume look like it is in the comics and have never shown Bruce Wayne actually wearing the make-up after he takes the mask off.



Revealing mistakes

As one of the Superman Squad runs up to fight Batman, he drops to one knee before he was even touched by Batman.

The immediate aftermath of Jimmy Olsen's shooting in Africa is shown through a video feed from an airborne camera, presumably from a UAV. The latitude & longitude of the UAV and where its camera is pointed are shown on the upper and lower right of the video feed. Both coordinates are nowhere near Africa, although they are in the vicinity of Creech Air Force Base in Nevada (a major hub for UAV operations).

In the obituary for Clark Kent, the opening couple of paragraphs are repeated further down the article.

Pearl necklaces of even moderate quality have a knot placed after each pearl, holding them in place on the strand. When Martha Wayne's pearl necklace is ripped, only one pearl should have come loose.

When Diana is watching the footage sent to her by Bruce Wayne, she slides her finger to the left on the touchpad but the cursor moves to the right.



Miscellaneous

While being interviewed on television, Senator Finch Holly Hunter is shown as being the Senator from Kentucky, only the "k" is lower case.



Anachronisms

The Jeep Renegade Bruce Wayne is driving at the beginning of the film (which takes place at the end of the Man of Steel film) had not yet been released (2014) when the Man of Steel movie was released (2013).



Audio/visual unsynchronized

One of the differences between the 'standard' and the 'Ultimate' editions are the fate of a news helicopter that stumbles upon the fight between Superman and Doomsday; in the first edition, as Doomsday jumps toward the Lexcorp tower, the helicopter is just able to swerve out of the way in time, while in the latter edition, Doomsday slams into and destroys the helicopter in his jump. However, the sounds of the helicopter successfully avoiding Doomsday's leap still remain in the background of the Ultimate Edition's version of the scene, despite the helicopter exploding in a ball of flame.



Plot holes

Some users have stated that Superman took 10 minutes to cross the bay to confront Lex because he was still weak from the kryptonite gas and moving much slower than usual. When Lex and Lois are on the roof of Lexcorp Tower, Batman's bat signal is visible in the distance and it is clearly only a mile or two at most. When the film shows Superman approaching the ship, he is clearly moving at an extremely high rate of speed that would have enabled him to cross the bay in a matter of seconds, even if he were weak. If you listen closely, there seems to be a sonic boom when it switches from Lex holding the timer to showing Superman approaching - a sound effect the director would not have inserted if he wanted the audience to think Superman was too weak to fly fast. Also, after Doomsday is "born," Doomsday throws a punch at Lex and Superman is able to go from standing to flying fast enough (and strong enough) to catch the punch in an instant.

When Batman rushes to save Martha Kent, time is of the essence, yet he still takes the time to change out of his suit of armor and put on his more traditional suit before even going there.



Character error

The prison guard instructs Lex to turn and face the wall and then place his forehead against the wall, "So I can come in and restrain you". A guard would never enter the cell of an unrestrained prisoner in this fashion. The prisoner would be required to place his hands through the aperture in the cell door to be handcuffed before the door was opened. It is possible that this instruction is a setup for Batman's arrival, but Lex would have almost certainly been suspicious of the breach in protocol by the guard.

At the LexCorp gala, Clark can hear what Bruce and Alfred are saying because of Superman's hearing range, yet he follows Bruce moments later instead of using Superman's X-Ray vision to track him.

The Spanish subtitles shown on the TV news flash at the party at LexCorp are incorrect. They read "La celebraci?nes ... fueron interrumpidos" whereas it should read "Las celebraciones ... fueron interrumpidas" (plural feminine without accent).

Superman, a person who can fly at absurd sub-light speeds, and throw baseballs around the world, decides to stab Doomsday face-to-face... rather than just hurling the spear at him (at super-speed, with super-accuracy, and super-positionality.) However weakened he was, he still had the power to fly, which means he was still.operating at (X)-human capacity.