Toby Fox’s indie RPG that became cult phenomenon. Kickstarter June 2013 ($51K raised), launched September 15, 2015, sold 5+ million copies, spawned massive fandom despite being made primarily by one person.

Subversive Gameplay

“The RPG where you don’t have to kill anyone.” Bullet-hell combat with pacifist options, breaking fourth wall, characters remembering previous playthroughs. Genocide route made players feel genuine guilt. Three endings (Neutral, Pacifist, Genocide) encouraged replays.

Cultural Phenomenon

“Megalovania” became iconic (100M+ YouTube views). Sans boss fight legendary difficulty. Papyrus spaghetti memes. Fanbase created 10,000+ AU (alternate universe) variations. Earthbound-inspired but uniquely charming.

Industry Impact

Proved solo indie RPGs could compete with AAA. Influenced Deltarune (sequel/spiritual successor), Omori, OneShot. GameFAQs Best Game Ever poll controversy (undertale fans raided). The hashtag celebrates anniversary milestones and AU creations.

Sources: Sales figures Toby Fox tweet, Best Game Ever controversy Polygon