I worked with a colleague who many years ago was fixing a PC and complained that it was not working when powered on. I took a look a litle later and the BIOS chimes were pretty much indicating "no ram". The box had 2 sticks of RAM in them so that is wrong. I took the sticks out and to my surprise, I saw 2 sticks of DDR which were in a slot where there should be DDR2. I was baffled as the notches are wrong, so I compared the chips and the notches were correct. My colleague came back I asked "how did you get these into the motherboard ?" and was told "it took some pressing, but they finally clipped in"
correct RAM and MB worked, RAM into an older bit of kit to test and it worked, so no real damage, just bewilderment on my behalf at how they didn't stop, but just persevered, and this was a colleague with years of experience in the support team - so not a PFY from college