[Ehkzu]

Honestly, Buffy is mainly fantasy. However, it wandered into scifi territory when she entered college and encountered The Initiative, a secret government military organization that treated the whole demonic underworld as a science fiction issue and treated it with science fiction stuff--primarily the behavior mod chip they put in vampires to "fix" them. And Adam was a science fiction monster/antagonist. And this plotline filled that whole season--4 I believe. Remember Buffy guessing that they gave the baddies a military moniker? And of course the best line of this plotline--when the manager of The Initiative, upon meeting Buffy, told her she thought the Slayer was a tale told by vampires and Buffy replies "I guess you were mythtaken."

Also, later on, the Nerd Trio were largely scifi in character, starting with the Buffybot.

So I'd talk about how these days the traditional hard demarcations between genres are breaking down--just as in art the line between painting and sculpture has been crossed and mingled often in 20th-21st century works of art.

Or how Gershwin commingled jazz and classical music in his compositions.

A lot of stuff still dwells within the old boundaries, but there has always been boundary-crossing by innovative creators in all the arts, ever since when.