EDIT: This has been hotfixed. Just for the heads-up.
Mwplus seems to be leading people on. This is most likely what he is doing. If you guys look closely at his screenshot, you can see the 4 pillars before the Skeleton King, that summon skeletons. He simple gets resistances/armor etc. and life regeneration. You set up a bot to keep you from going afk, and just stand in between the 4 pillars. Mobs will hit you continuously and every 15 minutes, you will get a Goblin to spawn. Given the circumstances, this is most likely not done on Inferno, however if you are built right, it can be managed.
1. Get/Equip a Puzzle Ring.
2. Reign Of The Black King - The Royal Crypts. (Probably Hell difficulty or lower, unless you are prepared.)
3. Go to the spot where there are four pillars that summon skeletons.
4. Stand in the middle.
5. Setup a bot to keep you from going afk. Probably use some kind of healing/survival ability every X seconds.
6. Go afk for ~5 hours. You should get a spawn every 15 minutes when the cooldown resets.
7. ???
8. Profit
Make sure you have health regen for maximum survival. Get lots of Vit / Resistances too, in my opinion. Not sure if people already know this, but this is what Mwplus is leading people on about.
I'm not sure who deserves credit on this, but I'm sure it's posted somewhere already.