Undertale Yellow is a free fan prequel to Toby Fox's indie hit seven years in the making, and it's just released to massive fan acclaim.

A group of performers played Megalovania, from Toby Fox’s game Undertale to the pope on Wednesday. A recording of the performance circulated widely on social media.

Undertale, the quirky, pixelated adventure game, became a smash hit when it came out because of its unique mechanism: You can talk to its monsters and show them mercy, rather than killing them.