The New York Times has an article about the reasons that kids like to watch the same film repeatedly and what effect it may have.

On balance, they think it isn't harmful and may even be good for them.

Of course, they're not talking about letting your two year old watch the Jason flicks over and over. However, if your kid watches Toy Story (ahem, Brue) or Jimmy Neutron, it looks like you shouldn't be too concerned about it.

The current theory is that kids actually continue to watch these films because they are not only enjoying themselves, but taking time to try and figure out what is going on in the film. Often, picking up details that adults miss.

One researcher draws the analogy to having a familiar book read to them. Further, another research comments that repeatedly watching the same video gives kids a sense of control they don't have in their daily lives.

As one would expect, researchers strongly suggest parents spend time with their kids watching the films, so that they know what is in them, and also to help kids through the tough parts (parental death in most Disney films, dinosaur attacks if they are watching Jurassic Park)

Of course, there is such thing as too much of a good thing, so don't let them watch forever.