Danmu弹幕
dànmù
"Bullet comments": viewer comments that fly across the video itself, a defining feature of how donghua is watched on bilibili.
Danmu, literally "bullet curtain", overlays timed viewer comments directly on the video, so a famous scene arrives buried under a storm of live reactions from strangers watching across the years. The format came from Japan's Niconico, but bilibili made it the default grammar of Chinese fandom: warnings ("front high energy!" before a big moment), running jokes, and gratitude walls at finales.
For donghua specifically, danmu is part of the release ritual. Premiere-day episodes of a hit like Link Click are effectively communal events, and studios read danmu density as a real-time engagement metric alongside play counts.