On the surface, it might seem like the Men in Black franchise would have no problem lasting beyond Will Smith and Tommy Lee Jones’ pairing. The adventures of secret government agents protecting Earth from alien threats is a novel high-concept premise. The MIB universe has plenty of rich sci-fi worldbuilding and it’s a global organization. In theory, when Smith and Jones could no longer star in Men in Black films, the studio could just replace them with another pair of mismatched MIB agents to keep the series going.

However, as proven by the 2019 disaster Men in Black: International, it’s not as simple as that. On paper, Men in Black: International seemed like a sure-fire hit. Chris Hemsworth and Tessa Thompson had proven chemistry from the Marvel movies and the change of setting promised to keep things fresh (as it turned out, it was just same tired gags across the world). It didn’t help that Men in Black: International’s producers interfered with the script so much during production that director F. Gary Gray wanted to disown the movie, but the main reason the audience didn’t embrace it is simply that it was a Men in Black movie without Will Smith and Tommy Lee Jones.

At its core, Men in Black is a buddy cop story. Those cops are fighting alien forces, but it still boils down to the same appeal as 48 Hrs. or Lethal Weapon in that it’s all down to the central dynamic. Will Smith’s Agent J is a fish out of water who’s recruited to work for MIB and paired up with veteran Agent K, played by Tommy Lee Jones. Throughout the movie, as with any buddy cop movie, these mismatched agents become best friends. Thanks to Smith and Jones’ pitch-perfect chemistry, a lucrative franchise was born.

After the original Men in Black movie arrived as a breath of fresh air, the initial sequel Men in Black II disappointed fans with a tired rehash of all the jokes from the first one. The belated threequel, Men in Black 3, offered a glimmer of hope for the franchise. While the second movie made it seem like a one-trick pony with a rigid formula, the third one proved it could shake things up by bringing time travel into the mix. This not only gave the filmmakers a chance to explore new storylines and concepts; it also offered an interesting way around Jones’ aging. By the time the threequel got made, he’d become too old to keep up with the physicality of UFO law enforcement. So, Jones was put into the framing narrative with a couple of fun scenes alongside Smith before being replaced by Josh Brolin’s spot-on turn as a young Agent K in the ‘60s.

Brolin’s role in Men in Black 3 proved that the franchise can survive with more than just Smith and Jones, and that other actors can join the cast and feel right at home, but there’s a big difference between recasting a role for the middle section of the movie and replacing the entire cast with generic original characters. Smith and Jones (and briefly Smith and Brolin) brought a unique energy to the original Men in Black trilogy. Replacing them with two other actors – even similarly well-matched stars like Thor: Ragnarok’s Hemsworth and Thompson – just won’t work.

The crucial thing in buddy cop stories is not just that each actor is perfectly suited to their individual roles, but that the actors also share impeccable on-screen chemistry – when one movie or TV show nails this, it’s nearly impossible to replicate with new actors in a reboot. Previous attempts to recast iconic buddy cop duos have fallen flat. The Rush Hour TV series didn’t make it through a single season without Jackie Chan and Chris Tucker. The Lethal Weapon TV series made it to three seasons, but not with its original star, and its versions of Riggs and Murtaugh paled in comparison to Mel Gibson and Danny Glover’s timeless dynamic.

When Sony’s servers were attacked by North Korean hackers in response to the Kim Jong-un assassination comedy The Interview, plans were leaked for a crossover between the Men in Black and Jump Street franchises. Although the leak seemingly killed the project, it could’ve been an interesting way to revitalize the formula of each franchise – but it only would’ve worked if the Men in Black side had Will Smith and Tommy Lee Jones and the Jump Street side had Jonah Hill and Channing Tatum.

It’s probably too late for another Men in Black movie starring Smith and Jones, as Smith is committed to a couple of other franchises now and Jones isn’t getting any younger, but that just means the franchise should be left alone. Sony will undoubtedly be tempted to reboot it again in a few years with yet another pair of actors taking on the roles of MIB agents, but the mythology of the Men in Black franchise isn’t strong enough to sustain it without the stars that made it so popular.