Bumpy forehead alien
After Star Trek: The Motion Picture updated the look of the Klingons with a bumpy prosthetic forehead, bumpy forehead aliens became commonplace in Star Trek, since it was an easy way to make human actors look a little bit alien.
Examples
- Klingons
- Talarians
- Cardassians
- Kazon
- Trill (first appearance only)
- Vidiians (not noticeable unless they're healthy)