THIS BUG WAS ENCOUNTERED IN SNAPSHOT 15W41A

For some reason, Minecraft decided to render every single chunk as the one I last built in. It also decided to render at least minecarts, skeletons, and players, as all of the blocks in that chunk that had been placed by a player.

[See attachment 1]
That massive orange mess over there? That's another player. There are actually 6 layers to those squares, two for arms, two for legs, one for the head, and one for the body. Note that different skins show up in different colours, mine is a dark-oak shade of brown.
Also note that some blocks, including redstone, hoppers, and beacons, are invisible in the other chunks. Also, after placing one beacon in another chunk where it should've been, then placing another block in the original chunk, all four beacons (although inactive) appeared in that particular chunk.
Also, see the blocks in the corners of each chunk? for some reason these were treated as their own chunk; placing a block in it made the game only render those corners.

[See attachment 2]
This bug reaches infinately, apart from either +0 or -0 in either the X or Z direction (I forgot to check which one).

[See attachment 3]
Notice that the heads and bows of skeletons stick out from the buggy mess. Skeleton and wither skeleton skulls placed in the world do not render, though.

There are also a few bugs that I didn't capture in screenshots:
The chest, trapped chest, and ender chest items rendered as isometric squares as large as my inventory. When placed in the world, they would not render, but ender chests would still create particles.
Whilst searching for blocks (the search term was probably either skeleton, minecart, furnace, or chest) in the creative inventory, there was an animated item that sort of looked like steam, that was unselectable and several lines below all other items.
Beneath the 'materials' tab of the creative inventory, you could see every (sticky or normal) piston placed in the world, lined up diagonally, and whether they were extended or not.

Attempts to recreate this bug have been unsuccessful, I suspect that it was caused by swapping from one snapshot to another - maybe from 15W41B to 15W41A?
Other people joining the world (through LAN) experienced none of the effects I did.