I have a hypothosis of what is happening involving Nibiru and the Anunnari.
I think that last time Nibiru occured, that evil Anunnaki noticing how weak the beings of our world are compaired to the 'god-like' beings the Anunnaki are. He/She/It decided to enslave the beings of Earth. As the Anunnaki have no physical form, it inhabeted the body . However some other Anunnaki stood up to it, and defeated it. They then sealed it in a sarcophagus made of crystal, and left it on Earth to banish it from their home. Then a magic seal was placed on it, so as long as the sarcophagus remained closed, it's evil would never be released.
Thousands of years later it was found the sarcophagus, and when they opened it the seal was destroyed, and the evil could spread. It manipulated them and attacked people. The conquistadors managed to regain control of themselves long enough to bury far below what would become Crystal Cove. As the seal was now shatered, having it closed, would no longer fully repress it's power but could still weaken it.
Then the Planispheric Disk was used it was marked with the location of the sarcophagus, so the Anunnaki could restore the seal on the sarcophagus. It was split up in hopes that it would not be found before then, and have the evil unleashed. However, the Planisphiric Disk was also linked to it's power, and it's weakened evil could be used through the disk pieces.
Ideas in my theory:
- Scooby is a decendent from the Anunnaki, so he could be the decendent of one of the Anunnaki that stood up against the evil Anunnaki. This could give him immunity to it's corrupting power.
- Professor Pericles could be the decendent of a servant of the evil Anunnaki, and when he and the old Mystery Inc found the piece, it twisted his mind to serve his ancestor's master. Same might be true for Porto the donkey.