Appeal is a broad term, but character designs should be visually interesting and possess some level of charisma or features that help the audience empathize with them. As one of the 12 principles of animation, it is fundamental to creating a successful animation.
As animators, we understand that a character doesn't need to be complex to have appeal. The term "appeal" also refers to making a character interesting and engaging for the audience. Two effective ways to achieve this in your character animations are by varying shapes and exaggerating your character's proportions.
(Below is a video that explains Appeal very effectively)
Look at the variation of shapes on Turbo KO
Marge Simpson's exaggerated hair
Finn from Adventure time. A character can have a simple design and still be appealing and interesting. In fact, having less details can often free up animators to explore dynamic animations.
Miles Moralis is a character with great recognizability and appeal. Take note of how dynamic and interesting his silhouette appears.
One great way to test if your characters have a variety of shapes and proportion that generates appeal is to see them in a silhouette. Notice how easily all of these iconic characters read in their silhouette.
In addition to character design, try to maintain good silhouettes during the animation itself. This will make your characters and their actions more legible for the audience.
Finally, good color is an important component to great character design. Here is a Color Theory Handout that could be a helpful resource when trying to make color choices with your character designs.
Find music for your Dance Party Animation Before you begin animating
You may choose whatever music you like, just be aware that if you use trademarked music, it may be more difficult to upload your work later to streaming or social media platforms. Alternatively, you can create audio using Garageband, creative commons sources, homemade browser/phone beats. There are links to several services below.