The Toons:

The Toons are a recreation of a Disney character such as Willy, Oswald, Disembodied, Ace, Impure Mouse, The Face, Ortensia and other unknown characters. Due to the Corruptus effect not being canon in 3.0 the Toons were probably satanic drawings that came to life. Most of the Toons kill humans and take their organs to use them for themselves.

UO:

UO (Also known as UWF) is most likely a actual God that was beyond earth and has now resided on Discovery Island for a very long time. She would at some point take in the Toons as her adopted children.

Story (Treasure Island):

The basic story of you playing as Jake and trying to find Henry who went missing. You would at some point meet UO and have a boss fight that involved The Face.

Story (Oblitus Casa):

Following the events from Treasure Island. The Face and most likely the other Toons have become more melted and showing more organs. Its unknown what else would happen in Oblitus Casa but it would've ending with a third game coming.

Story (Project D. I.):

Project D. I. most likely was the third game in the series that had no Five Nights theme and was original. Its unknown what else would happen in Project D. I. but it most likely would have ended the Treasure Island 3.0 series.