Di yi ci is a common Mandarin expression meaning the first time, and in short-form video it is often used less as a spoken sentence than as a label for a moment. Creators drop the brief clip at the start of first attempts, debuts and new experiences, where its plain, matter-of-fact delivery makes the setup feel immediate without needing a longer explanation. Its appeal online comes from that economy: one familiar phrase can frame an entire joke, reaction or milestone in under a second.