Mary's note changes slightly between the time she writes it and the time Jimmie reads it.
The position of the tree in the street between shots keeps changing. It is clear to the right in the initial direction of travel of the two cars, then it is to the left near the curb when the car crashes into it - in a position where Mary's car would have to have been driving on the sidewalk.
The stage doorman clearly vest-pockets his bribe as James Shannon enters to go backstage, yet he then has the money in his hand again when Shannon emerges to reclaim it. The doorman also pockets the money twice between shots.
While dodging the rolling rocks, the knees of Jimmie's trousers are out in some shots and intact in others.
Just as the horde of would-be brides overruns the college football game, one of the players can be seen throwing himself to the ground, already pretending to be trampled.
The handwritten notes, whether by James or his girl, or others, are all in the same handwriting, indicating they were written by the same person.
The boulders are clearly fake - one boulder hits James and bounces off of him.