From Diablo Wiki
There is a small chance for the dungeon to spawn in the cemetery, which will take up the unused fourth portal in the zone. The other three portals, randomly chosen, are versions of the Defiled Crypt. Development Hell shares the same tileset as the crypts, albeit it can spawn a bit larger than the usual crypt due to its content.
The dungeon contains zombies (skinny and fat zombies) who all bear a name of someone on the Diablo III development team, with the flavor text of the employee being their job title. There is a Feat of Strength associated with the dungeon for killing the Unburied version of Jay Wilson entitled Smash! Jay, Smash!.
Since the dungeon features so many unique zombies, it tends to run a bit larger/longer than the average defiled crypt spawn. In addition, the "fat" zombies will not spawn a crawling torso when killed, even though the animation will play indicating that the torso is present. Only zombies in the level have unique names. Skeleton and Skeletal Summoners may spawn, but they have no unique names or traits.