So they mention their neighbour's daughter "Suzy". Whilst it's not the same name, Toby Fox could've planned it to be spelled that way for Deltarune but changed it for whatever reason, possibly to not spoil the (theory technically) secret. In the Nintendo Switch version, Clam Goner mentions that "The time you meet her is fast approaching" and disappears with the sped up version of Gaster's Theme (from the Sound Test room)

So you've probably heard that people say that Deltarune Chapter 1 released the same year, but if Clam Goner is really connected to Gaster and mentions Susie (again, a theory)

...

Could this mean that Gaster is going to be connected to the Deltarune storyline...? I know that theory has spread around, but this one adds to the evidence.

Maybe Gaster is creating these timelines, or at least if he isn't, he's planning to connect with it somehow. Also, I have a feeling that voice at the start of Chapter 1 is Gaster, and the Vessel...maybe they're using it for something...

Anyways, that's all I wanted to say. Stay safe y'all!