Ever done this? The PCs show up to an adventure and find an NPC adventuring party has beaten them to it. They could be a Similar Squad, if you want to make it a running gag, or a different group of characters can just answer the same call.
This is something shared universes like the big superhero settings will actively avoid, so that Spider-Man can get to the secret lab when the alarm goes off without finding Captain America already there and handing the police an unconscious Electro. That kind of thing is only funny for a while.
Still, hearing about other adventurers’ deeds will make the hero business seem a bit less lonely.
On the other hand, when the PCs are adventurers for profit like dungeoneers, Shadowrunners or Ghostbusters, having a rival team chasing the same emergency and the same paycheck is a sure cause of trouble. Being shown up by an NPC party will definitely breed antagonism.
Which is of course the best time to force them to work together.
Having written this up, now considering what I could do with the idea in my current V20 game...