Originally posted by MrMindI mean, Superman, Darkseid, Batman and J'onn have all appeared in the Sandman series.
more importatntly, dc cosmo has been referenced in vertigo books multiple times too, as Gailman direct reference to the history of planet OA or RAO/krypton in endless night, Despair's convincing Rao to bring life on the unstable planet is literally the reason Superman exists.planet mogo appears in sandman overture
these kind of examples are countless (I would love you guys to post more on that, Phil? Galan?)
And in Seasons of Mist, Odin gives Morpheus a tiny dimension in which he has imprisoned the JSA and trapped them in a perpetual cycle of Ragnarok(from the "Last Days of the JSA" story.)
And of course, you have Destiny, Death, and Dream popping up in several DC stories over the years as well...