Most of you people are really something! Incapable of looking at the OPs photo and seeing that the center cartridge is, a with a near 100% certainty, a 9mm Makarov, not a 9mm Parabellum with a deep seated bullet! Look at the ogive, completely different that the others. Bullet is full diameter at the case mouth instead of showing a gap as it would be if it were the same bullet seated this deep. Case is shorter, hard to tell just how much but it sure isn't a 9x19. If OP had done two things, aligned the cartridges so they were all the same distance from the camera instead of angled away to the right side so there is some perspective acting on the image, and taken the shot level instead of looking down at an angle which distorts the case lengths and reduces the length difference! Deliberate? I don't know, but it could very well be, just to see what sort of silly responses the distorted photo would engender! Sure worked if that is what happened. Question for OP, did you happen to look at the headstamp on the odd cartridge? What does it say?
What would have happened if he had tried to fire it in his 9mm? Absolutely nothing! The larger bullet would have increased pressure over what would be expected from a 9x19, but nowhere to standard pressure of 9x19. Case mouth is nominally .004" larger than 9x19, but not enough to wedge the case in a normal 9x19 chamber. Most likely thing that would happen is an under-recoil and no ejection. In other words, a simple stoppage. Hardly the disaster that at least one poster flat stated would result in a blown-up gun! Give me a break.