The success of ever good romantic comedy boils down to one simple thing: chemistry! As our leads begin their journey to falling in love, through one unlikely scenario after another, the audience agrees to suspend all disbelief if they can just believe that the characters belong together, no matter what. Until recently, Hollywood’s on-screen love stories have had a narrow focus: if BIPOC and LGBTQ couples were seen at all, they were in dramas, not romantic comedies. In five years, a list of my favourite romantic comedy couples will undoubtedly include more diverse pairings.

Until then, here’s my current list of screen favourites with chemistry so potent they could have been made in a lab. According to Hollywood legend, Hepburn told her future co-star, “I fear I may be too tall for you, Mr. Tracy,” when they met on the set of “Woman of the Year” (1942), to which producer Joe Mankiewicz responded, “Don’t worry.

He’ll cut you down to size.” So began the journey of one of the most memorable onscreen couples in the history of film. (In real life, Hepburn and Tracy reportedly had a 26-year love affair.

) In total, the duo starred in nine films together, including Adam’s Rib (1949), “Pat and Mike” (1952) and “Desk Set” (1957). Even in their final movie, “Guess Who’s Coming to Dinner” (1967) — when the stars weren’t playing the leads anymore, but the parents — their chemistry shone through. Rom-com vet Witherspoon and Ruffalo (whose only other .