Quote Originally Posted by Immortal Hulk View Post
Maybe you already knows this, but I'll detail anyway. During Peter David's run, Banner was physically separated from the Hulk and, some time later, they had to be merged again because both were dying. To do so, the Gamma Base developed a nutrient bath where both Banner and Hulk would be submerged. An accident happened (General Ross tried to sabotage the process) and Rick Jones fell into the bath too.

As a result, Banner turned into the original Grey Hulk and Rick became a green, much weaker, Hulk.
These events didn't happen in PAD's run. Banner and the Hulk were separated via the Nutrient Bath in IH #315, which was done by John Byrne. His run was IH #314 - 319. He left and Al Milgrom took over with #320 and stayed until #330 (not counting the PAD fill-in with issue #328).
Milgrom remerged the two in #323, the color change from green to gray in #324 and the Rick Jones Hulk in #325.
When PAD took over, he spent his initial issues tying up loose ends from the Byrne/Milgrom issues (writing off the Hulkbusters, curing Rick, etc.) and going into his own, like the Ground Zero storyline.