All of these parodies take place in Hell.This is why Adolf Hitler is always suffering comically surrealistic misfortunes, because he has been sentenced to spending the rest of eternity as a Butt Monkey. This is why the setting looks like the 1940s, but is actually taking place during the 2000s and 2010s because of many anachronisms. And this is why nobody can grow older or stay dead permanently, because they've already died and are now just immortal souls. Hermann Fegelein might actually be Satan himself, who enjoys tormenting others so much.
Fegelein is a Time Lord......and he commits antics by using technology from his TARDIS. Also, whenever he regenerates he doesn't change form or identity at all, hence the illusion that he can't be killed.
The parodies are actually what happened to Hitler and co.The Führerbunker is actually a form of Year Inside, Hour Outside time machine from which all modern news, media, technologies, etc. can be accessed. Fegelein was accidentally corrupted by time travel, becoming his godly form and causing others to officially file him as dead. Hitler was getting more irritated by both the technology and the seemingly invincible Fegelein and eventually killed himself. Upon Germany's defeat in the war, Fegelein used his powers to remove all facts leading to the time machine's existence, as well as perpetuate the illusion that he's dead. This is also the real reason the Nüremberg executions took place: not to punish the Nazis for their atrocities, but because they wouldn't shut up about what happened to them in the bunker, thus preserving The Masquerade.
Hitler and co. are speaking a conlang.Designed by a German linguist, it sounds like German and some phrases of the conlang can be mistaken for German phrases. But don't be fooled: the language is very polysemantic and precise context is needed to understand it, hence it seems that words like "Fegelein", "Wenck" and "Verrat" have so many meanings. This is also why the parodies are always subtitled: only the people who were in the parodies could tell the translation.
Fegelein is behind the Space Nazi invasion.That's where he kept running off to, the Moon! And this is the source of all his pranks. And Gunsche, disguised as Klaus Adler, is helping him.
In Hitler Rants Parodies' planned The Final Conflict series, he will finally kill off Fegelein.HRP is responsible for making Fegelein an unstoppable immortal wizard. It would be refreshing to see him NOT surviving Hitler's final assassination attempt on him.
Professor Zündapp from Cars 2 is actually Fegelein.This would explain why he is able to turn into a car "without magic", as he claims in this video. Fegelein tampered with some dimension-travelling technology and winded up in the Cars universe in the form of a Zündapp Janus. He then gets hired by Miles Axlerod to help him destroy any cars using alternate-fuel. When the plan fell apart, Himmler showed up and broke him out of jail and brought him back to the Hitler parodyverse. He discovered that he now has the ability to change between human and car form at will, which he then happily demonstrated to the bunker staff, as shown in the aforementioned video.
Every single parody is canonical.It's just that Fegelein keeps using a time machine and screws things up on a regular basis, whether it be just For the Evulz or so he can forever keep playing antics on the bunker (as there's many videos where Hitler or some other character is either killed or broken beyond repair).