Maybe copy an easter egg from GDocs or an older word processor, or think of something ourselves. Word has a half-feature half-easter egg where if you type =rand(x, y) you get an amount of random paragraphs. One half-feature half-easter egg I thought of is maybe add a keyboard shorctut to rotate text upside down (
transform: rotate(180deg); display: inline-block;). Both are quire hard to implement, though, although both are more generally useful (text replacement and applying styles). But maybe we can think of something simpler.