Board Thread:General Discussion/@comment-26006155-20190131130037/@comment-26006155-20190308033953

WhatsYourExcuse wrote: We don't know for a fact that the door leads to the underground, or if the underground even exists in this universe. You mentioned earlier that the Donation Box that was supposed to be in the Dark World of Deltarune ended up in the garbage dump in Waterfall in the switch version of Undertale.

The world may have been warped somehow, but there's still an underground realm below the surface. And the creepy Gaster music that starts playing when you get near the locked door tells me something bad is down there.