Much like most movie adaptations of famous books, The Prince and the Pauper is no exception when it comes to leaving things out or adding things in during filming. Depending on which version of film you are referring to, you will be able to see many differences.
As for the few main differences that most of the film adaptations embody, the viewer can easily see what they might have in common, but I will list the three most popular differences found in many of the films, although not all are the same:
1) The first and most common difference between the book and the films is that the two boys, both the prince and the pauper, choose to switch clothes on a whim in the book. This is very difference compared to in the movies, where the two children (especially the prince) see it as more of a game to see if they would be able to pull off their very differing lives with success. In the book, it's quite obvious that when they are mistaken for one another and forced off into their separate directions, they are both quite upset at the mistake in identity and spend most of the book trying to convince those around them of who they really are.
2) In such movies as A Modern Twain Story: The Prince and the Pauper, it's apparent that the time and location of the story is very different from the book. You could even say it's a very stark difference. This is common for a lot of Prince and the Pauper adaptations, as writers may have wished to keep the story "fresh" and more appealing to newer generations.
3) Besides changing the date and location of the switch between a prince and pauper, oftentimes the main characters are not necessarily living on the streets as a pauper, but are simply living a life of poverty with a lower income family, if the movie is set in more modern times. The prince might also not be true royalty, but is instead an adolescent who was brought up in high society.
The following are similarities kept between the book and most film adaptations:
1) Once the prince and pauper have spent some time in each other's separate lives, they always end up giving up, seeking each other out to switch back in order to return to their former way of living. This is to play on the moral of the overall story, which is usually summed up as "the grass isn't always greener on the other side" or something to that degree.
2) No matter what adaptation, both boys always find that each other's lives are filled with their own hardships, such as the pauper living a difficult life of squalor and possibly even having to fight to survive each day, while the prince lives a life constrained and full of rules and regulations without much chance for independent freedom.
3) Most adaptations peg the role of pauper as a thief of sorts, which is usually what leads the two boys to meet one another or is used as an obstacle for the prince to deal with during his short lived time as the pauper.
Content will be erased after question is completed.