Undertale's 10th anniversary stream included new areas and changes to the original RPG that might just connect it to Deltarune even more, and fans are freaking out

Undertale is over a decade old but still inspires twisty fan theories and heated speculation to this day. And as if the last 10 years of wild theorizing wasn't enough, the game's official 10th anniversary stream decided to send fans spiralling further by including new areas and changes to the original indie hit that might just connect it to Deltarune even closer.

In Fangamer and developer Toby Fox's anniversary marathon stream, fans were quick to spot some sights that weren't exactly familiar. For one, there was an entirely new, moody area full of ruins. Then, even more weirdly, Gaster's super rare door which only unlocks under very specific conditions is in full color in the stream rather than its usual monochrome appearance.

Redditors quickly noticed that the stream's ruins seemingly also appeared in Deltarune's intro cutscene, with many speculating that this area, too, relates to the game's most mysterious entity, Gaster, since his theme pops up here as it does throughout Deltarune.

"Toby really knows how to ragebait," one YouTube comment said, referring to how the stream simply skipped past a detail that's sent multiple online forums into a frenzy. "This is f***ing insane," another online fan commented.

While this might raise hopes for future Undertale DLC or an anniversary update, it seems like all these additions were only made specifically for this stream. Though, with how heavily Deltarune teases the ever-enigmatic Gaster, we might just see the ruins expanded in the still-in-development game.

Toby Fox doesn't think Deltarune Chapter 5 "will be released in the first half of 2026" but there's some good news: "we don't have any external factors surrounding the release date this time. We'll release it when it's done"