#1: This list of acronyms will almost exclusively deal with various alternate realities that contain an Earth with a universe surrounding it that is similar to the one in which we live, and not alternate realities that are un-Earthlike in many significant ways, but which may have numerous dimensional counterparts that have nevertheless interacted with many such alternate realities containing an Earth in the course of their respective histories (e.g., Oz, Wonderland, the Dreamlands, etc.).
#2: One alternate reality that I have initially decided not to list below is the Warren Universe (WU), as certain research suggests that many, and possibly most, of the series characters who appeared in the nearly 20 year history of Warren comic magazines (primarily from EERIE, VAMPIRELLA, THE ROOK, and THE GOBLIN), as well as many of the self-contained stories, are likely to be part of the Wold Newton Universe proper, and thus may not currently require a seperate listing. I have personally conjectured that the many series and stand alone stories that appeared in Warren's 1984/1994 magazine may exist in various alternate future timelines of, or dimensional tributaries branching off from, the Wold Newton Universe and/or the Edgar Rice Burroughs Universe.
The same can be said for the "Kingverse," i.e., the interconnected works of Stephen King, as current research suggests that the above prose writings may also occur within the context of the greater Wold Newton Universe, and as a result, the "Kingverse" will not be given a seperate listing below.
#3: I WILL be listing the Star Trek Universe down below, despite the fact that much research (particularly much of the information to be found in the Star Trek novels written by Greg Cox, such as ASSIGNMENT: ETERNITY and the two EUGENICS WARS novels) suggest that the mid-22nd century to late 24th centuries (and beyond) that were seen in the various Star Trek series represents a prominent alternate future timeline of the Wold Newton Universe proper (in the two aforementioned novels by Cox, we got to see the Star Trek Universe of the late 1960's to the late 1990's, and there was much evidence provided therein to suggest that the Star Trek Universe proceeds directly from the timeline containing the "consensus" Wold Newton Universe of the late 20th century). I gave it a seperate listing for the nonce because Star Trek has a huge fan base all its own who may want to consider the Star Trek timeline to be a universe in its own right, but its inclusion down below at the present time is not intended to suggest that the Star Trek timeline is entirely seperate from the Wold Newton Universe proper, but simply to make note of the fact that it's sometimes useful to refer to the Star Trek Universe as if it were a "seperate" entity unto itself as a simple matter of convenience during certain ruminations about its numerous characters.
The same can be said about the Harlequin Romance Novel Universe, which will be given a seperate listing below, as many of those romance novels have an interconnected continuity. They may yet turn out to be a sub-set of the Wold Newton Universe proper, much as is the Warren Universe, the "Kingverse," and the "Buffyverse," but since so few creative mythographers have evinced a great interest in the romance novel genre thus far, there has not yet been a major attempt to connect any of the people and events from these interconnected novels with some of the prominent and established denizens of the Wold Newton Univese (but this may change in the future, as the field of creative mythography is dynamic and ever-expanding, and the Wold Newton Universe is probably the ultimate crossover universe, as Jess Nevins noted in passing in his book HEROES AND MONSTERS).
Note about the Image Universe: It should be noted here that what we often call the Image Universe is actually a "hypertime" based reality, possibly existing on a lengthy super-stream multi-timeline thread within the Omniverse, that routinely shares (and later dispenses) continuity with various alternate sub-universes, but which evidently does not exist in its own right, and the true nature of the Image Universe has not yet been fully explored by alternate reality researchers at this writing. There have been five known alternate sub-universes that were part of the Image Universe's quantum "family" in its known history, but at this writing only three still remain under the influence of its thread.
Initially comprising the Image Universe super-stream thread when that reality first became known to researchers, writers, and artists of the Real Universe in 1992 were the characters and attendant back stories comprising the WildStorm Universe, the Extreme Universe, the Highbrow Universe, the McFarlane Universe, and the Valentino Universe; due to the cosmically destructive Entropy event that once threatened all five interconnected and quantum-overlapping realities (all existing within a common "hypertime" super-stream thread), the Extreme Universe was permanently excised from that thread, and thus no longer interacts or periodically "crosses over" with the greater Image Universe multi-timeline, and for reasons unknown, the WildStorm Universe has likewise ceased interacting with the multi-timeline, as well. Hence, it can be surmised that the Image Universe is chaotic and in a state of perpetual quantum flux, with alternate timelines periodically entering and then subsequently leaving its omniversal hypertime thread. [End note]
Of course, all input from both the present and future members of the group will always be more than appreciated, and nothing about this list (which is by no means "official," but simply intended to be useful to the newbie) should be considered graven in stone :)
I will also list the first published (not chronological) appearance of each universe as currently known by this author, and some will represent educated guesses, and I by no means have the final word on this. Please note that I am NOT going to include multiversally or omniversally ubiquitous texts, such as Greek mythology, common to many universes, as the first appearances of any of the below universes, as that will get much too complicated, and the world mythologies are common to most alternate universes. This list will change and be ammended as different opinions are offered and more research is done. If I'm not sure where a certain universe first appeared (FA), I will list "uncertain." The listings that I believe to be largely guesswork on my part will have a (?) following them, and will be ammended upon a better suggestion by another member of the group.
MU= Marvel Universe
FA: MOTION PICTURE FUNNIES WEEKLY #1 [first Sub-Mariner]
DCU= DC Universe
FA: NEW FUN COMICS #6 [first Dr. Occult]
WSU= WildStorm Universe
FA: STORMWATCH Vol. 1 #1 [first Stormwatch]
DHU= Dark Horse Universe
ABCU= America's Best Comics Universe
FA: ADVENTURES OF TOM STRONG #1 [first Tom Strong]
WNU= Wold Newton Universe
FA: BEOWULF (?) [earliest written text I can find that took place in the WNU not including traditional world mythology]
ERBU= Edgar Rice Burroughs Universe
FA: THE MOON MAID (?)
ExU= Extreme Universe
FA: YOUNGBLOOD Vol. 1 #1 [first Youngblood]
HiU= Highbrow Universe
McU= McFarlane Universe
FA: SPAWN #1 [first Spawn]
ValU= Valentino Universe
IU= Image Universe
FA: YOUNGBLOOD Vol. 1 #1
AmU= Amalgam Universe
FA: DC vs. MARVEL #3
CGU= CrossGen Universe
FA: [pre-War version] Uncertain; [post-War version] KISS KISS BANG BANG #1 [first 'Sir Charles Basildon']
SLDCU= Stan Lee's DC Universe
FA: JUST IMAGINE STAN LEE CREATING BATMAN #1
SLU= Stan Lee Universe
GKU= Gold Key Universe
FA: MAGNUS, ROBOT FIGHTER Vol. 1 #1 [first Magnus]
DKU= Dark Knight Universe
FA: THE DARK KNIGHT RETURNS #1
DCAU= DC Adventures Universe
FA: "Batman: The Animated Series" Episode 1
MsU= Milestone Universe
FA: HARDWARE #1 [first Hardware]
NU= New Universe
FA: STARBRAND #1 [first Starbrand, Ken Connell]
UU= Ultimate Universe
FA: ULTIMATE SPIDER-MAN #1 [first 'Ultimate' Spider-man]
TCU= Top Cow Universe
FA: WITCHBLADE #1 [first Witchblade]
FA: PRIME #1 [first Prime]
CU= Chaos Universe
HRU= Heroes Reborn Universe
FA: FANTASTIC FOUR Vol. 2 #1
PTU= Parallel Time Universe
FA: "Dark Shadows" TV series (soap opera, exact episode # difficult to determine)
OTRU= Old Time Radio Universe
STU= Star Trek Universe
FA: "The Cage" [first Christopher Pike, Spock; original series pilot]
RU= Real Universe (a.k.a., "Earth-Prime")
HU= Hasbro Universe
FA: "Transformers" TV series Episode 1
CVU= Crossoverse [a.k.a., "Crossover Universe"]
FA: MARVEL TREASURY EDITION #2 [Superman meets Spider-Man]
MSU= Movie Serial Universe
STVU= Super-Hero TV Universe
FA: "Superman vs. the Mole Men" [big screen film which led into "The Adventures of Superman" TV series]
ADU= Anno Dracula Universe
FA: ANNO DRACULA
HRNU= Harlequin Romance Novel Universe
Note about Toho Universes: All begin with "Godzilla, King of the Monsters"; hence, I will list the first time each appears as a distinct divergent universe
STU= Showa Toho Universe
FA: "Godzilla Raids Again"
HTU= Heisei Toho Universe
FA: "Godzilla 1985"
MTU= Millennium Toho Universes
FA: "Godzilla 2000"
XTU= X Toho Universes
FA: "Godzilla Against Mechagodzilla"
HBGU= Hanna-Barbera Godzilla Universe
FA: "The Godzilla Power Hour" animated TV series, Episode 1 ("The Firebird")
SDU= Showa Daiei Universe
HDU= Heisei Daiei Universe
FA: "Gamera, the Guardian of the Universe"
DU(i)= Interim Daiei Universe
FA: "Super Monster Gamera"
SWU= Star Wars Universe
FA: "Star Wars, Episode IV: A New Hope"
XEU= X-Men: Evolution Universe
FA: "X-Men: Evolution" TV series Episode 1
MMU= Marvel Movie Universe
MTU= Marvel's Transformers Universe
FA: TRANSFORMERS #1 [Marvel Comics series]
MAU= Mars Attacks! Universe
FA: MARS ATTACKS! Trading Card Series
WNU(a)= Alternate Wold Newton Universe
MADCU= Marvel and DC Universe(s) [when making a reference regarding both of these seperate yet subtly interconnected universes]
AU= Alternate Universe
AF= Alternate Future
PU= Pocket Universe