D.Y1: This is NOT Your Story!

On 12/04, part two of the Undertale-Deltarune theory was released. As of writing, there have been no clues discovered within this video. However, for completeness, the following hidden information was found.

During the intro, text written in the Wingdings font appeared. After decoding, it turned out to be

the secret to my existence 
is in these next few words.
never gonna give you up, I’m
never gonna let down. I’m never
gonna run around and hurt you

GASTER
i think you will find this very interesting

which is basically just a Rickroll.

Also, at approximately 8:02, text flashes across the screen. The text was decoded to be ALITY backwards, likely forming the full text REALITY.