Yuuzhan Vong
The Yuzzhan Vong are a species humaniod sapients of extra-galactic origin in the Star Wars Expanded Universe. Externally they resemble humans to a degree but are distinguished by their sloped foreheads, grey-and-yellow skin, and short noses. Yuzzhan Vong society is highly religious and is divided into a number of castes -- including Warrior, Priest, Shaper (Genetic Engineer) and Intendant -- each with its own culture and its own gods. Masochism is a common element throughout Yuzzhan Vong culture, and headscars are considered a symbol of rank in their society. Yuzzhan Vong technology is biological. They are notable for launching an invasion of the Star Wars galaxy in 25 ABY.
Fan Reaction
In general, the fan reaction to the Yuzzhan Vong has been negative, largely because of biowank.