Now since one of the upcoming issues of PKNE was rumored to be some sort of crossover with DoubleDuck, I was starting to wonder how all of these events fit in with one another.
So far, we know of quite a few series that all happen within the same universe. Obviously the first two series are directly followed by PKNE, with Pikappa being some sort of parallel universe. (I should note at this point that I have only read up until Bankers translation and have only heard about the crossover crisis that seems to happen in one of the later issues.)
But that's not all. We also know that PKNA was a direct follow-up/spinoff of the Junior Woodchucks/Giovani Marmotte. This was made clear in PKNA 0/3 "Xadhoom" when the nephews mention traveling from the Arctic to Africa, which was an event that happened in the third issue of the ten-part storyarc "Minaccia dall'infinito" by Sisti.
So, when we factor in the origin stories of the Duck Avenger from "Paperinik il diabolico vendicatore", we have the following timeline.
Timeline 1: PK Classic -> Giovani Marmotte -> PKNA -> PK2 -> PKNE
Timeline 2: PK Classic -> Universo PK
Timeline 3: PK - Pikappa
So where's DoubleDuck in that timeline? Does it happen in between PK2 and PKNE? Is it another parallel universe? There was one strip where DD and the Avenger appeared simultaneously, and another panel where the X-Transformer was seen, but A) are these canon and B) are they from the main universe?
Feel free to join in, and most importantly: Correct me if I forgot something. Maybe there are other stories that we already know are from the same continuity. These are just the ones I'm aware of.
EDIT1: Added Universo PK.