* Stylization: Cartoonists use simple shapes and exaggerated features to make characters easily recognizable and appealing. Swirls on elbows are an example of this, adding a touch of whimsy and personality without being too complex.
* Emphasis: The swirls can draw attention to the character's movement, particularly when they're bending their arms or performing actions. They add a visual cue that helps the viewer understand the character's posture and motion.
* Visual interest: Swirls add visual interest to the character's design. They break up the monotony of a solid-colored arm and make the character appear more lively.
* Humor: The swirls can be seen as a humorous detail, adding a bit of playful absurdity to the character.
* Tradition: In the early days of animation, the swirls may have been a common practice, and it's simply become a convention that has been passed down through generations of cartoonists.
Ultimately, the reason for the swirls is likely a combination of these factors. They contribute to the overall look and feel of the character, adding a touch of whimsy and personality.