Klingon

In a parallel universe, the Klingons were a species who were allied with the United Federation of Planets during the 24th century. One Klingon, Worf, was a Starfleet officer who served on the USS Enterprise. (IDW: Assimilation²)

Biology
The Klingons were humanoids with ridged foreheads.

Behind the scenes
The Klingons are one of the major races of the Star Trek universe,. They have appeared many times in all six television series and the majority of the movies.