John Wayne made not one, not two, but three Westerns with director Howard Hawks about a sheriff defending his office from outlaws.

Between 1959’s Rio Bravo and 1970’s Rio Lobo, the duo shot 1966’s El Dorado, which co-starred Robert Mitchum as the drunken lawman opposite Duke’s gunslinger.

Interestingly, Wayne had replaced Mitchum just a decade earlier in 1955’s Blood Alley after he was fired following a feud with the producers.

The two co-stars became good friends and their humour can be seen in how they fixed an on-screen gaffe during principal photography.

Mitchum’s sheriff JP Harrah had been wounded in the right leg and needed a right-handed crutch. However, he switches this to the left in a scene when he’s driving a wagon.

The story goes that Wayne made sure that his character Cole Thornton mentioned that this had happened in one of the film’s final scenes to fix the continuity error.

Director Hawks loved this so much that he left it in the movie as a wink to the audience. However, Mitchum’s retelling of what happened is slightly different.

Mitchum said that he objected to switching the crutch to maintain continuity, but that Hawks had insisted so that it looked better in that scene.

However, when the director saw how bad this looked in the dailies, the star suggested that additional dialogue be added at the end of the movie with Wayne’s gunslinger to cover for the mistake.

So, in the final scene, both characters can be seen having their crutches under the wrong arm.