Call of Duty: Modern Warfare 2 Remastered (opens in new tab) lets you revisit the campaign with fresh visuals, and you'll be rewarded with a special Trophy for your attention to detail in the first mission.
All you need to do to earn the Trophy is start the first mission, S.S.D.D., and make your way through the training course. Once you get to The Pit, you'll see General Shepherd standing up on an observation platform to the left of the entrance between two soldiers. All you need to do to avert his tragic betrayal is line it up and take the shot. Of course, it still counts as friendly fire at this point, so you'll fail the mission and start over at the last checkpoint. But then you'll see the "Precognitive Paranoia" Trophy pop up to reward you for your time-traveling vigilance.
This is a followup to Modern Warfare Remastered's famed Time Paradox trophy, which rewarded you for paradoxically sniping Makarov in Chernobyl back in 1996 before he could take his proper place as the big bad in the Modern Warfare sequels. It turns out Modern Warfare 2 Remastered has another call back (or call forward) to Modern Warfare 3 in its new version of No Russian.
In the course of playing Modern Warfare 3, you take control of Yuri as he tries to prevent the airport massacre perpetrated by Makarov's ultranationalists. He ends up passing out from blood loss as he witnesses the tail end of the atrocity. It was a bit of a ret-con because you never saw Yuri at the airport in Modern Warfare 2 - but now you do.
As you can see in this video, after riding down the escalators near security you can turn to the left and see Yuri stagger forward a bit before dropping. You can also shoot near his feet to make him pop back up, but I don't think that's meant to be canonical.
It looks like Call of Duty: Modern Warfare 3 Remastered could follow in not too long (opens in new tab) - I wonder what timeline-ruining Trophies that one will include?