Many fans have pointed out photos from the set of The Mortal Instruments: City of Bones movie in which Jamie Campbell Bower is seen with the Fearless rune marked on his body. As we all know, this would be a major film faux pas because the Fearless rune is created by Clary in the next book in the series, City of Ashes.
When asked about this, Cassandra Clare responded on tumblr by saying that movie mistakes are expected (she mentioned in another post that the Shadowhunters’ Voyance runes were originally in the wrong place as well). However, the Fearless rune issue was caught early! The actors will not longer have it painted on, and the Fearless runes already filmed on the actors will be removed in post-production.
Movie mistakes are bound to happen, but that’s one less thanks to observant fans!