This will be a collection of crossovers discovered throughout the fanfic. Enjoy!
I got these all directly from Nev themselves for the family trees*
Sandra Wu-San: From New Earth; is Tankhun, Kinn, and Kim's bio mother*
Oksana & Eve: from Killing Eve; part of the Mikailov clan*
Neal: from White Collar; Vegas and Macau's bio dad
Trogdor: from Strong Bad Email #58, titled Dragon. Trogdor the Burninator. (credit for discovering crossover: kat8cha in comments of chapter 1)
Katya and Sofia (including Goncharov reference): from Goncharov (credit: multiple comments on chapter 3)
Boris: based similar to Toothless from How To Train Your Dragon (credit: happy_chicken comment on chapter 3)
Mischa: adaption of Gwyn ap Nu (credit: nev responded to kaejaebae's comment on chapter 4)
DumDum Kim: Chapter 5, Kim showcased a side similar to Jeff's music video persona in Dum Dum (credit: happy_chicken's comment on chapter 5)
Max, Woody, Jet: from BOC's The Hidden Character (credit: happy_chicken's comment on chapter 5)
Ken/Mek & Tawan: follows KinnPorsche first production canon where Perth (the actor) was casted as Tawan's brother (whose name is Mek). (credit: nev's response to 99_9's comment on chapter 6)
Kinn & Jin Zixuan: their commonalities (credit: nev's and 99_9's comment convo on chapter 6)
Wolf puppy developmental stages are based on actual books and scientific articles that Nev researched themselves (credit: nev responding to frangiblefealty's comment on chapter 2)
Werewolf's wolf aging with the moons inspired by another fanfic (the first 3 months of puppy life). Everything else is Nev's creation~ (credit: Nev responding to peachyM00's comment on chapter 2)
"The concept of a werewolf's wolf aging with the moons is inspired from a cool bandom fic from back in the day, but that fic only covered the first 3 months of a puppy's life. Everything else - the culture, evolution, behavior, social dynamics, fertiles vs. non fertiles - that's all me and i'm very proud of it." - Nev
Batman exists in NRNRB (credit: nev responding to tsttoain's comment on chapter 3)
Wild hunt: Gwyn ap Nudd is "a Brythonic warrior-hunter God of the wilderness and ruler of Annwn. ... During winter he leads the dead and spirits of Annwn out into the world on the Wild Hunt, and every May Day he fights against his eternal rival, Gwythyr, for his beloved, Creiddylad."