Semi Frequent Undertale Factsさんのイラストまとめ

*At the start of Chapter 2, if you save instead of leaving the Dark World to gather everyone, it will have the regular CH1 save point visuals.

Submitted by: @Magicmakerman1

* During the 6TH Anniversary Live Stream, you can see how instead of removing the one black pixel, he added another one. This however isn't in the original version, not even in the Steam Version.

Submitted by: @gustyMoment

* During the 6TH Anniversary Live Stream, the Fangamer crew played a modified version of Deltarune that includes some jokes, here are some examples.

* In an OST Rip of Toby Fox's Halloween Hack for Megalovania, you can find a quite old comment from Toby Fox explaining his thoughs on Megalovania 10 years ago (at the time this was posted).

Submitted by: @EelsGayTwompson
Source: https://t.co/oturc1Dw3d

* Tsunderplane seems to wears a hat very similar to Touhou's Yukari Yakumo. Taking in mind Yukari is Toby's favorite Touhou character, he probably wanted to fit her in somehow.

Submitted by: @YEPmultii
Source: https://t.co/P5HsA9A7DQ

* The "END" in Dwellers Empty Path is (a game made by Temmie Chang) uses the same font used for Undertale's title.

Submitted by: @NotDannyB1

* Asriel Dreemur's design resembles Sariel from Touhou: Highly Responsive to Prayers. The name Asriel also can be an anagram of Sariel. Both are considered Angels of Death too.

Submitted by: @KirbyEarthbound

* Toby Fox stated that his Minecraft skin is Garfield with Sans's Jacket with a glowing eye.

* If you somehow talk to Papyrus in Snowdin after Alphys's Date but before he calls you, he'll say this, however since it isn’t normally accessible in-game, the text goes unused.

Submitted by someone who didn't want credit.