A smiley face with animated eyebrows demonstrates core D3.js DOM manipulation. The code builds the face by selecting the SVG and appending grouped shapes—a yellow circle for the head, an arc for the mouth, and circles for the eyes. It then animates rectangular eyebrows using chained `transition().duration()` calls, moving them up and down in a loop triggered by the `on("end")` event. The example uses D3 v5 and relies on the `select`, `arc`, and transition APIs, with a separate `myBundle.js` file adding a gray background and a looping rectangle animation.