The Crawling Eye (real name Bob Keith) was the ruler of the Nightmare Dimension and one of the members of the 10 Dimension Leaders. He was the primary antagonist of the Nightmare Dimension Arc of UnMario: The Series.
The Crawling Eye is a very quiet and stoic character, only smiling or laughing when he deems necessary. He is extremely sadistic, and will not hesitate to kill one of his henchman just for fun. He also seems to be a masochist, as he revealed to Mario that he gets spikes in his eye on a daily basis to win a bet with Wario and Waluigi, who rules the 9th Dimension.
The Crawling Eye is simply a gigantic eyeball with two tentacles protruding from his top, and three others on one side each, and one on the back. He has a smaller eye in the middle, which seems to be his weak point (especially after getting it stabbed by Wario and Waluigi through everyday). That's pretty much it.
Role in UnMario: The Series
The Crawling Eye makes his first appearance in the Nightmare Dimension Arc, of UnMario: The Series, as a shadow in episode 323, where Nightmare Kaori tells him about Mario and the gang. He makes plans to exterminate them.
While The Crawling Eye is not present in the next few episodes, his voice is still heard controlling the Nightmare Doppelgangers and leading Mario and the gang through the Maze of Eyeballs.
He is finally seen again in episode 344, where he is harvesting power at the town's gates. He is absorbing all the souls of the gang (which were absorbed a few episodes earlier) and is trying to use them to make him even stronger. However, it is a long process, so he orders his Nightmare Dopplegangers to attack The Gang.
When Mario finally arrives a few episodes later, The Crawling Eye kills Nightmare Kaori, and then proceeds to battle Mario, however Mario is too weakened from the fight with Nightmare Kaori and after a few minutes of fighting falls down. The others however, get up and face The Crawling Eye, and defeat him by dawn.