Spencer Tracy and Katharine Hepburn. Humphrey Bogart and Lauren Bacall. Adam Sandler and Drew Barrymore? Like it or not, Sandler and Barrymore may be the closest thing this generation has to an “iconic” on-screen couple. In their new romantic comedy, Blended, they play an unlikely pair of platonic acquaintances who find themselves falling in love as the movie progresses. Not unlike The Wedding Singer. And sort of like 50 First Dates.

While the comic duo may not bring the same fiery fun and passion that their predecessors did, it could be worse. They could be Nick Nolte and Julia Roberts! Chemistry is a strange thing, indeed, and while it may be a science in most worlds, in Hollywood, it’s more like a game of chance. But if more than a century of movies has taught us anything, it’s that there are some definite rules when it comes to the chemistry of chemistry. These are The Dos and Don’ts of On-Screen Coupling.

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