Sim, parece que o Sr. Dark é uma homenagem a Morpheus
Do Wiki das Fábulas :
While Dark Man's name does not come from any specific story, it is clear that his presence carries out in various panels of literature, folklore and mythology, having collected names such as the Bogeyman, the Dullahan, the Khokhan, the Buse, Mörkö, The Dunganga, The Abo Ragl Ma Shokla, Burned Man, Lake Man, Buback, Torbalan and too many others to mention. However, he bares a striking resemblance to Sandman's Morpheus, and may have been based off of him.
Além disso, neste artigo :
It’s a wonder then how little mention was made of the writer Bill Willingham’s wink and a nod to Fables’ influential “predecessor”, Vertigo’s “Sandman”. “Sandman” started off with it’s God-like main character freeing himself from the prison he’s spent a long time in and going on a quest to gather his items of power. [...] What has happened in “Fables” then, was that it’s creator, Bill Willinghem decided to have a massively powerful being awakened from it’s year-long confine and dealing with the beings that have usurped his power since.
E olhe para esses dois painéis lado a lado:
Mas dizendo que ele se parece de alguma forma com o Dream of the Endless, essas duas figuras não têm muito em comum: Morpheus está interessado apenas em sonhos com os mortais, muito raramente entra em nosso mundo com outro objetivo além de visitar pessoas particularmente interessantes. O Sr. Dark, em contraste, está tentando subjugar o mundo, ou pelo menos as fábulas que vivem neste mundo.
Além disso, vale a pena apontar que o universo Fables está totalmente separado de outros DC / Vertigo, enquanto muitos personagens de "Sandman" interagem com personagens de outros livros - Death conheceu Lex Luthor, Batman esteve em Morpheus Wake, Destiny conheceu Superman etc.