In this animation it uses the 12 principles of animation.
One of the principles it uses is anticipation. It shows this when Luxo Jr pops the Pixar ball and walks off screen sadly and Luxo stares at the flat ball. This creates anticipation because you are waiting to see what Luxo will do but then Luxo Jr comes in with a large beach ball.
Another one of the principals the animation uses is Squash And Stretch. This is show When Luxo Jr is bouncing on the Pixar ball and it squashes under his weight then stretches back when he jumps up from it.
It also shows the Principal of appeal. This is show with the characters of Luxo and Luxo Jr. It is appealing because everyone knows the Pixar intro with Luxo and this animation gives the people who watch Pixar a little insight to his life.