Warning: SPOILERS to follow for Deadpool 2!
Unlike Avengers: Infinity War or a new Star Wars episodic film, Deadpool 2 isn't exactly the kind of movie you would have expected to have part of its plot shrouded in secrecy. However that turned out to be the case when the true villain of the film, who was absent from the marketing, showed up. The production went to extreme lengths to keep the film's secrets, including Juggernaut, from being spoiled, but it was almost all for naught thanks to a visit from a legendary rock 'n' roller. Guns N' Roses lead guitarist Slash visited the set and created huge spoiler risks, as Ryan Reynolds explained on the Deadpool 2 commentary:
Slash showed up and the crew lost their fucking minds. Rightly so, Slash is a legend. Suddenly all of these pictures of Slash were on peoples' phones with like, Juggernaut in the background and like, 'No guys! You can't post any of those! Or at least photoshop the crap out of them!'
Cell phones with cameras, social media and fandom make for an especially spoilery combination. It sounds like there are some major Guns N' Roses fans in the Deadpool 2 cast and crew, and they were so caught up with meeting Slash that they neglected to pay attention to what else was in their photos. It would be an easy mistake to make if you weren't thinking about it, and were just caught up with meeting a rock legend and wanting to get a great picture. Juggernaut is pretty hard to miss and recognizable too, so it's not like people wouldn't know what they were seeing if the photos got out into the world. Even if they photoshopped the character out, depending on their photoshop skills it might be obvious, evidence of absence and whatnot.
What's funny about this is that the Deadpool 2 team was already being crazy protective with the scripts to make sure they didn't get out and secrets like Vanessa's death and the Juggernaut weren't revealed, and all of that was almost spoiled because everyone was freaking out over a rock star. It's crazy how productions like this, as well as things like Star Wars, MCU films and Game of Thrones, all take major precautions to prevent spoilers, and the littlest thing has the potential to undo all of that. Fortunately, for most people I think that Juggernaut's role in the film came as a surprise. There were clues that he would be in the film ahead of time that some people picked up on, but the fact that Ryan Reynolds was playing him came as a surprise even to the cast.
Maybe there will just be no cell phones on set for Deadpool 3 or X-Force, just in case. Also, Slash should totally have totally gotten a cameo as one of the people trying out for the X-Force. Maybe next time.