Michel Koiter
At the Shrine of the Fallen Warrior, there is a memorial dedicated to an orc with the initials "M-K". M K was Michel Koiter, one half of Twincruiser, a Blizzard illustrator who passed away during the development of World of Warcraft. If you visit the memorial, you will find a spirit healer named Koiter. Most likely named in dedication for the once beloved man.

Peke Utchoo
In Mudan Grotto there's a skeleton called 'Peke Utchoo', which sounds quite similar to the Pokémon Pikachu. Whoever put the skeleton in also included a note that reads, "If anyone shall ever find me, I hope I am able to bring them to laughter." The note was probably put in to make sure that the player realizes that the skeleton is meant to be a joke.
[edit]Other Pokémon References
Encountered during the Main Quest, there are a few locations which reference Pokémon in their names. In Ilunibi, there's a section called Marowak's Spine. In Arkngthand, there's a Weepingbell Hall. In the Urshilaku Burial Caverns, there is a section called Kakuna Burial.