14th Cosmos
The 14th Cosmos was one of the universes known to the Crew of the Copper-Colored Cupids. The SavageMen were native to it.
Cupid Fact File #598 predated the Incident Report on the late-2019 Skirmish at the Cupid Theatre and described the 14th Cosmos and its “anomalous properties”. Its contents were apparently sufficiently well-known for a reference to the 14th Cosmos to be introduced to the script of The Moonbeams in the hope that Cupid viewers would make the connection to the 14th Cosmos's anomalous properties and thus shrug off the accidental plot holes introduced by the cartoon's juxtaposition with The Death? Planned It! regarding the backstory of the purportedly-fictional SavageMen.
Shortly after the premiere, however, a temporary Rift opened between the Cosmos and the Cupid Homeworld, allowing a group of real, live SavageMen to enter Judicator-337's office. Resolving the copyright dispute between Sketchbook-430 and Paintbrush-122 regarding the design of the SavageMen as seen in the cartoons, the real SavageMen asserted their ownership of their own copyright, as apparently affirmed by “the Supreme Court of the Fourteenth Cosmos”, before departing again through the Rift, which subsequently closed. (PROSE: Plagiarism of the SavageMen)
Behind the scenes
As Plagiarism of the SavageMen was a satirical riff on a then-ongoing controversy in Doctor Who fandom regarding the Cybermen, the cartoons The Death? Planned It! and The Moonbeams are named as comical analogues for the first two Doctor Who episodes featuring the Cybermen, entitled The Tenth Planet and The Moonbase. In the latter, the Cybermen claimed to have previously encountered on “Planet 14”, an apparent misremembering of the Cyberman planet's numbering as “the Tenth Planet” in the earliest story, which would go on to raise many questions in later Who works attempting to address the continuity of the Cybermen.
Although the SavageMen are real within the 14th Cosmos, it has yet to be clarified whether it also houses real versions of other elements of the Rainbow Adventures series, which is usually depicted as purely fictional in-universe as far as most references to it in The Crew of the Copper-Colored Cupids are concerned.