Minecraft wiki entry for Mob, associated text: Renaming a mob "Dinnerbone" or "Grumm" using a spawn egg or name tag causes it to flip upside down.
Renaming a sheep "jeb_" makes its wool change color with a smooth transition between colors. Note that the sheep named "jeb_" drops only the color of wool it had when named (e.g., when a pink sheep is named "jeb_" and then sheared when its color has changed to blue, it still drops pink wool).
Renaming a vindicator "Johnny" makes it attack all nearby mobs, except other illagers.
Renaming a rabbit "Toast" gives the rabbit a new texture, as an Easter egg to xyzen420's girlfriend's missing rabbit.[7]
Spiders, cave spiders, slimes, silverfish and illusioners are some of the few mobs that can see players behind walls.
Cats and villagers can see players with the invisibility effect.
There are many blocks in the game that do not take up a full block, such as trapdoors, and mobs actually see many of these as full blocks.
With some blocks, mobs mistake them for air, such as carpets, snow, and string.