Vaults in Fallout are no strangers to horrific experiment -- according to the lore, that's why vaults exist in the first place. Vaults were constructed for social experiments, the likes of which couldn't be carried out in any other circumstance.
A few vaults in particular happened to mess with cloning technology. One vault, for example, arbitrarily decided to clone a random guy over 50 times. Thing is, the cloning tech developed in the world of Fallout isn't perfect. Scientists could make copies of people, but these copies weren't exact. In this case, the random guy that was cloned over and over didn't function like a normal human being. Instead, all of his clones became maniacal, hostile men that could only say one word: "Gary".
ShoddyCast is back with their newest instalment of Fallout lore, and this time they dive deep into the ethically dubious things that certain vaults did. If you have six minutes to spare, you should give it a watch:
Worth noting that the video starts out with an unrelated short about Grognak the Barbarian, which you might know as the protagonist of all those comics lying around in the wasteland. It does go on to talk about cloning in Fallout though! Skip to the 1:10 mark if you want to get straight to that.