Alternate Creature Interpretations (Feel free to add your own additions)

[Sizzlefoot]

Also, does anyone else think that the duergar are redundant? "These are dwarves, known for their deep mines and being grumpy, except even deeper and meaner."

Yeah, they are. Probably because they were inspired directly by Norse dwarves (sorta), while more "normal D&D" dwarves closely resemble those from Tolkein more. Since Tolkein basically just used Norse dwarves but with the positive aspects played up a bit, duergar end up pretty redundant.