The image to the right is a concept art of Cthulhu done by Tiy. It was previously thought that the development team intended to add the boss in an update, but it is unknown if this is still planned. Rumors exist that it will be added in Terraria 2.
- The concept of Cthulhu was popularized by author H. P. Lovecraft in the 1900's. Today, this creature is a popular element of Lovecraftian Horror. He also said he didn't even know how to pronounce Cthulhu.
- He is missing one of his eyes. This is because of the Eye of Cthulhu, which was destroyed earlier on. However, if the pattern is followed, Cthulhu should have no brain on Crimson worlds, as the Brain of Cthulhu is destroyed as well.
- The Moon Lord boss added in the 1.3 update bears resemblance to Cthulu, and may have been intended as the Terrarian version of him.
- It is confirmed that he is the Moon Lord's brother.