Hollywood is full of tantalising “what-if?” moments; decisions made on the spur of the moment that have far-reaching repercussions for all involved. What if Robert Zemeckis had persevered with Eric Stoltz on the Back to the Future set, rather than bringing in Michael J Fox? What if Tom Selleck had played Indiana Jones instead of Harrison Ford? What if, as initially wanted by the film’s producers, Robert Altman had directed Alien?

And now we can add another big mystery to the list. What if David Schwimmer had starred in Men in Black instead of Will Smith?

Apparently, as Schwimmer revealed in a recent podcast episode, this was originally the plan. When he was offered the MiB part, Friends had been on the air for a few years and Schwimmer was the hottest thing around. However, he had just starred in a film – 1996’s The Pallbearer – that was a critical and commercial disappointment, and wanted to try his hand at directing instead. He lined up a film with Miramax called Since You’ve Been Gone, just as the offer came in for him to star in Men in Black. He was left with a difficult decision, and history has already recorded his choice.

Arguably, it wasn’t the right one. Since You’ve Been Gone ended up being downgraded from a theatrical release to a made-for-TV film that few remember, while Will Smith got the Men in Black job and became an instant megastar. “Look, I’m really aware, whatever 20 years later, maybe more, [Men in Black] would have made me a movie star,” Schwimmer sighs on the podcast. “If you look at the success of that film and that franchise, my career would have taken a very different trajectory.”

Or would it? It might be easy for Schwimmer to look upon Men in Black with envy. It might have even caused him to view Will Smith’s subsequent successes as his own. After all, in the early 90s they were both just well-liked sitcom stars. Maybe Schwimmer would have gone on to star in I, Robot and I Am Legend instead of Smith. Maybe he would have scored huge hits by recording the theme tunes of several of his films. Maybe, even, he would have played Muhammad Ali or flamed out at the Oscars. Who can possibly say?

Except that isn’t really how it works. As easy as it is for Schwimmer to say that Men in Black would have made him a star, it’s equally possible that Will Smith made Men in Black a hit. He didn’t come out of nowhere to get the role. In the two years prior to Men in Black he had made a pair of genuine blockbusters in Bad Boys and Independence Day, plus he was carefully branding himself as an all-round singing and dancing entertainer. His next film, whatever it would be, was always going to attract a lot of attention.

Meanwhile, Schwimmer had The Pallbearer (which opened at No 9 at the US box office upon release), and with the exception of the Madagascar series, hasn’t really proved himself to be much of a box office draw. Anyone remember All the Rage? Picking Up the Pieces? Duane Hopwood, the 2005 film about a man called Duane Hopwood? Which isn’t to say that these are bad films or that Schwimmer is bad in them, more that they didn’t land on the same level as, say, Hitch.

It’s also genuinely impossible to imagine Schwimmer as Agent J in Men in Black. Try it now. Smith’s swaggering cool defined that role, and swaggering cool isn’t something that Schwimmer has in much abundance. He can be anxious and knotty and play out of his depth extremely well, but try to imagine him throwing on a pair of sunglasses and telling Tommy Lee Jones “I make this look good.” Really try. Try and imagine him saying it unironically. Try and imagine him saying it without a question mark at the end. It’s truly impossible.

Which isn’t to say that Schwimmer should be beating himself up about this missed opportunity. It’s 2024. Smith has become an international punchline thanks to his loss of control at the Oscars, and his career will never fully recover. Meanwhile, the enduring success of Friends – a sitcom he made 30 years ago – means that Schwimmer still receives $20m (£15m) a year in re-run fees without having to lift a finger. Sometimes, regardless of your bad decisions, the universe has a way of making everything OK.