In spoofing his own hit movie, Edwin S. Porter produces a fairly creative parody that is worth seeing in itself, and that is perhaps even more interesting in historical terms. "The Little Train Robbery" is a re-working of the classic "The Great Train Robbery", with all the characters changed to children, and most of the settings miniaturized accordingly.
The story often parallels the original quite closely, and the more familiar you are with the original, the more similarities you can spot. So this is more than just one of the era's common remakes of the one-shot films that had become popular - it involved a detailed look at the original movie, with many choices as to how closely to follow it. It is certainly one of the most detailed examples of this kind to be found in the first decade or so of cinema history.
There are also times when, in contrast to the original, details are changed to play up the fact that the characters here are all children. As such, it is interesting in terms of the age-old debate as to how far behavior, especially of the young, might be influenced by the movies. Attitudes always change from one era to the next, and not always in the same direction. Attitudes in past eras were not always as simple as we may assume them to have been, and this is the kind of example that provides an interesting perspective on the issue.
Seen simply as a movie, this is not one of the best of its era, but it has some clever features, and it still works well enough. To the audiences of the time, to whom "The Great Train Robbery" would have been one of the very best movies they had ever seen, there would probably have been noticeable interest in this parody version.