The funny part is when you walk in the corruption and hold a 'suspicious looking eye' Cthulu spawns. Same thing if you hold worm food The eater of worlds spawns.
I've noticed that too. Me and Bust3r once got 5 EoC's in a row because of that one bug. Shit was cash! Later on though, it got me killed because EoC spawned a split second before i used the eye. Baww.
Some of the new things confirmed from the artist of Terraria is the removal of cobalt armor and replacing it with grass armor, it being a completely different set with new bonuses.
Also, the big one, -costumes-.
I'm not sure if you can design this yourself but I'm sure you can, they are basically like skins in minecraft. They will cover armor and you will keep the same stats as you usually have.
Well I created a giant block of ebonestone jutting out the roof of my house, spawning literally hundreds of Devourers, Eaters of soul's, Cthulu, and the Eater of Worlds.