Once upon a time, a long time ago, people figured out that they could draw pictures in a row and create the illusion of movement. This was called animation, and it became a really popular way to make movies and TV shows.
In the 20th century, which means the years between 1901 to 2000, animation got even cooler! First, people started making cartoons that were really funny and silly, like Mickey Mouse and Bugs Bunny. These cartoons were so popular that they became famous all over the world!
But then, people started doing even more amazing things with animation. They used computers to make cartoons that looked even more real and lifelike. They could even make 3D pictures that looked like they were jumping right out of the screen!
Some of the most famous 20th-century cartoons are things like Snow White, The Lion King, Toy Story, and The Simpsons. These cartoons are still around today, and people still love them just as much as they did when they first came out.
So, in summary, 20th-century animation is when people used drawings, computers, and special effects to create cartoons and movies that looked really cool and made people laugh and smile.