Often when an entity's name is in the chat, a tooltip appears when hovering your mouse over the text. It shows the name, entity ID and UUID of the entity, but the entity IDs have changed in snapshot 16w32a. For example, ArmorStand has now become minecraft:armor_stand. This has not changed on the tooltip though.
Steps to Reproduce:
1. Type the following command in the chat. Make sure you're an operator on a server or have cheats enabled on a singleplayer world. This command will make you say all entity names in the world.
2. Hover your mouse over one of the entities that are not players. Notice that the old entity IDs are used.