YMMV / Star Trek: The Next Generation S4E18 "Identity Crisis"

• Franchise Original Sin: This is the franchise's first real example of a story where a main character starts transforming into some other species, leading to a Race Against the Clock to discover how to cure them before the change becomes permanent, with later examples of this storyline including some of the franchise's more infamous episodes (such as "Threshold" on Star Trek: Voyager, and "Extinction" on Star Trek: Enterprise). As with a lot of other story types that were accused of being over-used by the latter part of the Berman era, this episode gets away with it mostly just because it did it first, and the execution was reasonably effective. It also helps that the cure in this case is relatively straightforward, instead of the more convoluted ones we saw later.