Throughout the movie Wayne's hat changes from white to black back to white and then black again.
When Quirt pushes between the men at the bar, the bartender pours him a drink and then leaves. The owner then arrives asking for some calm. As Quirt leaves the bar, the bar owner can be heard from behind the Baker brothers still imploring them not to fight, but it is the bartender who can be seen.
When walking down the street for the final showdown, the sun starts off to Quirt's right casting shadows to the left of screen, then a close shot shows shadows which could only come from a near-overhead sun, and then at the saloon the sun is coming from Quirt's left casting shadows to the right.
A dance hall girl pushes a spectator down onto a gambling table which collapses under him, with the only damage being to the legs of the table. In the next shot, the table is still collapsed but there is a large section of the edge broken off.
When Quirt arrives at the saloon, its entrance is in shadow. When Hondo and Laredo come out, they are in full sun.
The story is that Quakers on the frontier did not own guns. This is inaccurate. They would have needed guns for hunting. Beyond this, Mrs. Worth serves venison for dinner.
Laredo Stevens tosses Quirt Evans a small pouch that's supposed to contain "five thousand dollars in gold". When Evans empties the pouch a bit later, it has about a dozen coins or so in it. The highest value coin the U.S.ever minted was a twenty dollar gold piece. It would have taken 250 coins to equal five thousand dollars. The pouch held, at most, three hundred dollars.
In one scene a hand-cranked ice cream maker is used. As the farm is at the edge of Monument Valley, the availability of ice in that location and time period would have been virtually nil. Beyond this, although the ice cream maker is covered with a blanket, it is obvious that there is no mechanism.
Penelope's mother tells her to,"card the wool on the loom." Carding wool means to take a pair of wool cards (a pair of wooden paddles covered in metal pins) and brush the raw wool so as to ready for being spun into yarn. The loom can only used after the yarn is made.
Mrs. Worth tells Penelope, "You can card your wool at the loom". Carding wool is a means of combing out the fibers so it can then be turned into yarn at a spinning wheel. The loom is used to weave the yarn into fabric. While some might think that the carding statement seems a bit odd, it is possible that they might have the raw wool, wheel and loom in the same place.
Bradley brags to his friends about his and Quirt's exploits in Dodge City, when "the Earps and Clantons were feuding." But the Earps and Clantons fought in Tombstone, AZ, not Dodge City, KS. This is not a goof. The fellow was lying and showing his ignorance in doing so.
In the next to the last scene in the movie where the Marshal (Harry Carey) shoots Hondo and Laredo, he kills them with two rapid shots before they can shoot. In the reverse it shows the Marshal cocking his lever action rifle. It would be impossible to fire two shots so rapidly if you had to lever the rifle between shots.
When the wagon hits a severe bump it is obvious that "Penelope" is a dummy that is firmly tied to the seat..
The doctor at one point mentions "living in a never never land," an obvious reference to Peter Pan. However, the play did not see its first performance in London until 1904, and the novel was not published until 1911. There is no way anyone living on the 19th-century American frontier could know of Peter Pan's home.
At one point Quirt's double-breasted shirt is partially unbuttoned. You can see the small metal snap which is normally hidden by the collar. Snap fasteners were invented in Germany in 1885 but they did not appear on western shirts until 1901. Apparently the director had noticed the shine of a snap because in other scenes the metal snap was painted to match the shirt.
At approximately 8:00 the doctor passes the lamp to Penelope. A thick black electrical cord is clearly seen dangling from the lamp.
The Indian and horse sculpture on the piano in the saloon was not period, but an early 20th century nostalgia piece. A representation of an Indian with raised weapon on a galloping horse would have been extremely offensive to those who lost relatives in violent encounters with Indians.
The doctor refers to,"living in a never-never land." This is a reference to Peter Pan; a story that would not appear until decades later.
When Penny wheels the wagon around to pick up Quirt at the beginning of the movie, you can see an extra set of reins coming out of a small "window" that is visible below the wagon seat where the actual wagon driver (the stunt driver) is controlling the team of horses.
When Quirt and Randy was chasing after Laredo and his gang during the stampede, Quirt is heard to yell "hey Hondo" when riding up to knock Laredo out of the saddle. Hondo was another member of the gang.