Charlie, disguised as a tree, enters a pipe to escape a German. When the German tries to pull Charlie out, he separates the lower part of the tree costume along with Charlie's shoes. When Charlie emerges from the other end of the pipe, he is still wearing shoes.
When Charlie is disguised as a German officer and meets the Kaiser, he hastily buttons up his tunic wrong. But when he goes outside, it is buttoned properly.
Charlie, in his trench, throws the Limburger cheese into a German trench. This would not have been possible because the distance between the two sides' trenches ("no man's land") would have been far too great.
In the woods, where Chaplin runs to hide from the pursuing Germans, automobiles are visible traveling on a highway on the horizon.