Board Thread:General Discussion/@comment-26006155-20190425222457/@comment-26006155-20190511180709

PersonThePerson wrote: Okay, so let me see if I’ve got my timelines straight.

Sans (Frisk) and Gaster hide as monsters and Gaster does cool stuff. But then Gaster tries to murder everyone so Sans murders him! Then, Sans and Papyrus go back in time, splitting the timeline. New Gaster dies (Sans probably kills him, thus removing Ambassador’s reset contradiction) and in his death, his memory gets erased. Then, Sans and Papyrus wait for Frisk, who might have gotten amnesia from the existence wipe...but wait. I thought Frisk and Gaster arrived at the same time! Mostly right, except for Beta Gaster's memory getting erased. They make a fountain for him after all.

Although it does look like Frisk/Beta Sans gets his memory timed out after taking a head wound before Undertale begain.

There must have been some adventure Frisk went on, before Undertale began.

The fountain proves that Gaster, and Sans, arrived in the Underground before Chara did. So they definitely met her during the Alpha timeline. Which itself is an epic story waiting to be told.

Then something happened, and Frisk, alone, ended up in the Ruins wearing the bandage. Waking up on Chara's grave.