Star Trek: 10 Character Fates Worse Than Death
3. Contracting A Space Disease That Devolves You By Unlocking Dormant Genes
There are tons of Star Trek episodes dealing with some version of a space plague, which almost always infects all but one crewman. In the Next Generation episode "Genesis," the crew of the Enterprise encounter just such a plague, and the only one who isn't affected is Data.
The disease was accidentally created by Doctor Crusher in an attempt to help Lieutenant Barclay, but instead, she activated all of his dormant introns, and from there, the rest of the crew is infected by a disease that effectively begins regressing everyone's evolution by unlocking their dormant genes.
For Worf, he gets hot and aggressive... Well, more aggressive than usual. Deanna gets cold and begins to devolve into whatever Betazoids evolved from originally. For humans like Riker, it's a quick trip back to being a Neanderthal, which takes his intellect, but other humans are affected in different ways.
Barclay turns into a spider, and eventually, Deanna becomes an amphibian while Data's cat Spot turns into an iguana. Overall, it's one of the strangest episodes of the series, and thanks to some quick thinking by Data, it's all back to normal by the end of the episode but had he failed, everyone would have been stuck as some weird version of whatever their species evolved from.