Re: Let's say Marvel and DC were to merge universes.
Gaiman's version of Death appeared in Incredible Hulk
418, at the wedding of Rick Jones and Marlo Chandler. Peter David asked permission from Gaiman who approved, but PAD was ultimately given an odd condition about how she appears.
Read about it here (second legend down).
Whatever you celebrate this time of year-- be it Christmas, Hanukah, Ramadan, Kwanza, the Solstice, Life Day, Durin's Day, Festivus or whatever, let it be happy, joyful and safe.