Prior to Pike shooting the stagecoach's "shotgun," there is a "wide shot" of the travelling stagecoach. There is clearly a passenger riding in the right-rear seat. Yet, when the stagecoach comes to a halt (in the studio) after Pike has shot both the driver and "shotgun," there are no passengers to be found.
After Billy cut himself with Hoss's knife and wants to return it, Hoss says "why don't you use it until I learn you how to use it."
Although Julia Adams is listed as a guest star in the opening titles, she does not appear anywhere in the film.
When the boys are fighting, Orville repeatedly says, "say it, say he is a murderer or eat dirt." The first time you hear it, it is obviously an audio dub, as Orville's mouth is not moving.