A smiling cartoon face is rendered as a yellow circle with black-outlined features, including eyes, eyebrows, and an arc-shaped mouth. The eyebrows animate by moving upward and then back down over two seconds. The example uses D3.js v5 with React, building SVG shapes with `select`, `append`, and `arc` for the mouth path. Transitions are applied via `transition().duration()` to create the eyebrow movement.