The now-classic Groundhog Day flirts with (and breaks) the rules of multiple movie genres: romantic comedy, time travel narrative, small town dramedy, spiritual redemption tale—and it’s also given birth to an entire subgenre of its own. The “Groundhog Day episode” is a mainstay of many television series, and the plot even pops up in films, novels, and short fiction. It’s a fun way to play with established characters, putting your faves through the emotional wringer while trying to solve a murder or stop a crime. And it can be an equally effective tool for riffing on entire genre tropes; mixing in high school drama, slasher horror, or other well-worn genres can lead to some fascinating mashups. And in (almost) all cases, the…