Although play is irreducible, games repeat. Beyond the serial repetition that characterizes industrial forms of mechanical reproduction like newspapers, comics, novels, and films, in the case of videogames the microtemporal speed of serial interfaces and massive scale of serial distribution operate both below and above the horizon of conscious experience. As such, the serial operations of videogames structure, enclose, and ultimately alienate the technical processes of play from the conscious knowledge of the player. In their essay, “Digital Seriality: On the Serial Aesthetics and Practice of Digital Games,” Shane Denson and Andreas Jahn-Sudmann characterize the diachronic sequencing of serial interfaces and synchronic consumption of videogames as “digital seriality.” This essay explores digital seriality through the history and practice of tool-assisted speedrunning, a form of metagaming that stages a ludic intervention at the level of serial interfacing and subsequently disrupts the collective serialization of videogames as a mass medium. From the operations of the NES-4021, a parallel-to-serial shift register that governs controller input in Nintendo Entertainment System, to the history of moSMB.wmv, an early speedrunning video by Morimoto that went viral in 2003, tool-assisted speedruns transform twitch-based platform games into turn-based puzzles and single player experiences into massively multiplayer online games by playing the serial interface.