The Warriors series is incredibly long, with each book published in a relatively short span of time. As a result, mistakes often appear in the novels, the images, and in the official website devoted to the series. This article documents many of these mistakes in The New Prophecy arc.
In the previous cover, Brambleclaw is shown on the cover with green eyes.
The book repeatedly states that four seasons have passed since the events in The Darkest Hour, but this is not possible, as The Darkest Hour took place in leaf-bare, while Midnight starts off in greenleaf; the delay is rather six seasons.
Rowanclaw is mistakenly listed as a she-cat in the allegiances.
Graystripe is mistakenly mentioned as a RiverClan cat.
Feathertail is mistakenly mentioned with a flecked gray pelt.
While Mistyfoot is talking to Leafpaw and Sorreltail about the disappearance of the four cats, she tells them Feathertail and Stormfur had always undergone scrutiny about having a father in RiverClan, yet Feathertail and Stormfur's father was actually ThunderClan, and their mother was RiverClan.
The allegiances contains many mistakes, including the absence of the Tribe of Rushing Water, Rowanclaw's gender again being female, and Sorreltail being listed as Sorrelpaw, despite earning her warrior name in the previous book.
Tawnypelt is mistakenly said to have amber eyes, even though she has green eyes.
Purdy exclaims "Great StarClan" but it is established in Midnight that before he meets the Clan cats he does not know of StarClan, so it is unlikely he would use this phrase.
Leafpaw describes three cats from ShadowClan attacking ThunderClan; Russetfur, Cedarheart and a tabby tom. She explains that Cedarheart attacks her but then in the next sentence he is described as being in a fight with Brackenfur.
Brambleclaw states that he scented rabbits before the eagle attacked, but this was never mentioned before now. 
Leafpaw mentions that only she, Firestar, Graystripe, and Cinderpelt know about the fire and tiger prophecy, when two books previously Firestar had told Sandstorm about it.
Tawnypelt is mistakenly called Tawnypaw twice in the book, even though she has had her warrior name since Firestar's Quest.
There is a word missing from a page. A sentence reads: "...lit up the ThunderClan's golden pelt. He (Firestar) lay very still with his eyes closed." when it should say, "...the ThunderClan leader's..." Also, with that comes Firestar mistakenly called golden, instead of ginger.
Crowpaw is mistakenly called by his warrior name when he is still an apprentice at the time.
Tawnypelt is mistakenly called pale bracken-colored.
Brightheart is mistakenly described as having a 'tortoiseshell splashed coat' when she is in fact ginger and white.
Leafpaw describes seeing 'white and ginger fur flashing through the undergrowth'- later, this is revealed to be Sorreltail and Brackenfur, neither of which are white and ginger (Sorreltail is tortoiseshell and white, Brackenfur is golden-brown).
As Squirrelpaw and Sorreltail run past the abandoned camp, the description reads "If they [the monsters] weren't careful, they'd tumble right into the ravine and smash themselves to bits on Highstones"- likely they meant the 'Highrock' as Highstones is far away from the ThunderClan camp.
Squirrelpaw easily opens the catch to the cage when freeing Leafpaw from the monster, but without any instruction she shouldn't know how.
Firestar claims he and Ravenpaw have been through so much together, specifically referencing the death of Bluestar, yet Ravenpaw was not present for this.
The description reads at one point, "[Leafpaw was] waiting for the sickening crunch of fur and bone" but only bone would make a crunching sound, while fur would not likely make much noise even if crushed.
Leafpool comments on the day of the quarter moon that the medicine cats will be meeting at the Moonpool that night. However, medicine cats meet on the half moon, and in the next chapter Brambleclaw remembers that Leafpool had just paid her half-moon visit to Moonpool.