If you watched Disney animated films on repeat as a child, you probably had an inkling or suspicion that some of them looked a bit familiar.
Say, for example, the bear from Robin Hood - who looked almost identical to Baloo from The Jungle Book. Well, that wasn't an accident. The process is known as xerography and, as it turns out, quite a few Disney animated films used the process as a way of saving time and money.
You have to remember that CGI wasn't even an option and all of the artwork you saw in these films was hand-drawn. Therefore, that'd mean that new cels and animations would have to be drawn each and every time if, say, someone moved or was dancing.
So, what's the alternative? Re-use the animation at its base core for certain scenes. This video details just a few of the most well-known examples, but there's literally hundreds of scenes that have been harvested and reused, not just by Disney, but by Warner Bros. and Hanna-Barbera Cartoons.
Take a look.