For most games, patch notes that read "Updated on Steam to fix bugs and increase compatibility" would be a nonstarter. Ignorable. Useless.
But Undertale [official site] is not most games. More importantly, Undertale's community is not like most communities. And thus Undertale's Patch 1.001 bug fixes and increased compatibilities have been picked apart over the last couple days to reveal secret spaghetti or other such nonsense. Spoilers ahead.
Most of the changes are just small dialogue tweaks and stat changes, but one seemingly-insignificant encounter has Undertale fans clamoring. Here, I'll let you look at it:
The gist: You know Sans? Fat skeleton? Follows you around? In Sans's lab there are some drawers. Talking to a certain character (Clamgirl) now unlocks new descriptive text for the first drawer—a photo of three people with the words "Don't forget" scrawled on the back.
There are two prevailing theories. First (and most boring) is that the picture is of Sans, Papyrus, and Clamgirl. More interesting is the "It's Gaster!" theory. Gaster, if you're unaware, is a hidden character in Undertale—and, the theory goes, the lost brother of Sans and Papyrus.
Listen: Delving into the weirder side of Undertale is a bit like stumbling into one of those conspiracy rooms you see on TV, pictures tacked to the wall with bits of twine strung up between them like a game of Cat's Cradle gone wrong. Everything has meaning. Everything is important.
But the point is, people think Toby Fox is dropping little bits of Gaster into the game, one piece at a time. The new patch also makes it so a previously-hidden room, accessible only by manipulating the game's files, now has an infinitesimally small chance of appearing during a normal game—further legitimizing the whole Gaster saga.
I can't wait for Patch 1.002, wherein "Small bug fixes" turns out to be an entirely new Gaster-centric game, accessible only by turning around clockwise six times and then shoving microwaved spaghetti into your eye sockets.