Basically, the main rule in the GESB is "anything goes," as long as it abides by the rules in the first post in this thread. Your character can be from any universe or continuity that you want; a couple characters that I've had are from Animorphs-related universes, but not necessarily canon. My character Guppy, for example, is from a continuity where the Yeerks won the war, while my character Nepek is from roughly the same continuity of the Animorphs books, and Cletus isn't even related to Animorphs at all. The people who have been in this RP for years (Myitt, Terenia, and Luke being the longest-standing that are still active IIRC) have pretty much developed their own continuity with a bunch of original characters through the GESB and a few spinoffs, but I haven't even begun to pick any of it apart. Not sure if it's even possible to understand
everything that's happened in the GESB
And if anything doesn't make sense, it's pretty easy to handwave away with "the Bartender did it."
I'm not really sure what all is going on at the current moment, aside from my current character, Cletus, having just sat down with Aluminator's character Al and Gaz's Julius and Morgan. I tend to pop in and out a lot, so I'm not really sure what else is going on either XD