This is a possible summary:
The speaker claims that Sans and Papyrus are the two halves of Gaster's split brain, based on their personalities, abilities, and connections to the time-space continuum. He provides evidence from the game's details, such as their fonts, puzzles, humor, handedness, and knowledge of different timelines. He also suggests that Papyrus is not as naive as he seems and that he may have access to Gaster Blasters. He concludes that the SkeleBros can never fix the machine or restore Gaster, and that this adds a layer of tragedy to the game's story.
Here are the key facts extracted from the text:
1. Gaster was the Royal Scientist before Alphys and he speaks in hands.
2. Gaster only appears in certain timelines and he was shattered across time and space by falling into his creation.
3. Gaster's name is a combination of two fonts: WingDings and Aster.
4. Gaster has a connection with Sans and Papyrus, who are also able to manipulate gravity and use Gaster Blasters.
5. Sans and Papyrus are the two halves of Gaster's split brain, with Sans being the left brain and Papyrus being the right brain.
6. Sans and Papyrus have different personalities, puzzles, humor, handedness, and language skills that match their brain hemispheres.
7. Sans and Papyrus appeared out of nowhere and tried to fix the machine that shattered Gaster, but they failed.
8. Sans and Papyrus wrote "never forget" on a picture of three smiling faces to remember their origins and Gaster.
9. The text is a transcript of a Game Theory video about Undertale.