Extreme alien makeup - untypical for Star Trek shows. Usually, a yellow skin means android, pointy ears means a Vulcan alien ... Ferengis have giant ears and huge bumps for heads. Their spirit changes dramatically in later episodes. In this episode, they are characterised as warmongers, permanently armed with whips. In later episides in TNG, Deep Space Nine and Voyager (!), they become greedy monsters. Their confusing, inconsistent entrance in this episode might be intentional: If you, as a race, have something to hide, you mischaracterise yourself. As warmongers, if you think you can retain that image. Else you'll get blown to pieces. The Ferengi possibly misjudged the Federation's potential to annihilate the Ferengi. After all, unlike Romulans and Klingons, the Federation don't have cloaking devices with their space vessels.
Review of The Last Outpost
