He is mentioned later in "You Forgot Your Floaties." While inside Magic Man's mind, Betty witnesses a memory of him and Grob Gob Glob Grod discussing GOLB at an unknown date in the past. It is revealed that GOLB attacked Mars at some point and "took" Magic Man's wife, Margles. Grob Gob Glob Grod believes that GOLB will return and Magic Man agrees, using the threat of GOLB as a pretext for building a security system on Mars that takes the shape of Margles. Later, Magic Man changes his mind, claiming that Grob Gob Glob Grod is wrong and GOLB is "probably not coming back."
In "Come Along With Me," Betty, Maja, and Normal Man summon GOLB to Ooo, and he wreaks havoc by combining the candy people's mass to create hostile wraiths. Upon seeing him, Ice King has a flashback to an indeterminate date in the past when he researched GOLB as Simon. In the flashback, Simon describes GOLB as a "mysterious entity who embodies chaos," and states that "his presence is felt in every crevice where chaos lurks." When GOLB arrives, he swallows Finn, Betty, and Simon. Simon and Finn manage to escape before he digests them, but Betty stays behind to try to use the Ice Crown to wish GOLB away from their world. Her first wish to destroy GOLB fails because GOLB's power supersedes that of the Crown, but her subsequent wish for "the power to keep Simon safe" succeeds and allows her to merge with GOLB into a single entity. The newly-created Betty-GOLB exits Ooo, leaving the Ice Crown behind.
GOLB has a massive muscular red body and a cubic head topped with a pyramid with the bottom half fraying upward. He has four round yellow eyes with green pupils, with the two eyes on top slightly larger than the two below. Up close GOLB has cracks around his eyes and mouth. He has a forked tongue that is large and purple. His hands have three fingers and his feet have two toes and one dewclaw. He has orange-yellow talons on his fingers and toes.
After fusing with Betty, GOLB's appearance is altered, appearing as giant and red with a cubic/pyramid head somewhat similar in appearance to Grob Gob Glob Grod's but the shape appears to be that of Betty and her clothing, and their eyes are blue and green instead of yellow.
After GOLB "took" Margles, Magic Man traveled to Prismo's Time Room and wished that she would return, but Prismo was unable to successfully bring her back. GOLB's powers make him one of the most powerful entities in the multiverse, even magic power of Evergreen's Crown can't defeat him. GOLB most likely traps his victims inside of his mouth as mentioned in "Temple of Mars" and attempted in "Puhoy" although Finn managed to bounce off of GOLB's tongue. In "Come Along With Me," GOLB is shown digesting things he eats by returning them to their original form. This is why Betty was able to make a wish with the Crown. GOLB was also shown to release a dangerous gas from his mouth which causes beings to become wraiths infused with discord.
As GOLB is the embodiment of discord, his ultimate weakness is harmony. In "Come Along With Me," GOLB is weakened by the characters singing "Time Adventure"; this suspends GOLB's creations and tears a hole through GOLB, which allows Finn and Simon to escape digestion.
- GOLB's name was originally revealed by Adam Muto on Spring. It was later officially revealed in "You Forgot Your Floaties."
- GOLB may have attacked Mars at Olympus Mons because that is where Magic Man planned to install the defense system meant to protect Mars from him.
- GOLB's backside appears in promotional art for "Astral Plane."
- In "Whispers," The Lich refers to himself as the last scholar of GOLB, though the exact meaning behind this, as well as the full nature of his connection to GOLB, is unknown.
- GOLB's ability to erase things from existence is possibly related to his personification of entropy and chaos, given information lost to entropy is unrecoverable.
- There are several similarities between GOLB and Grob Gob Glob Grod:
- GOLB's head has a shape similar to that of Grob Gob Glob Grod's headwear.
- Finn meets GOLB when he dies in the Pillow World. In "The New Frontier," Jake claims that Grob Gob Glob Grod rules Glob World, where people in the Land of Ooo go when they die.
- Both have four of a certain body part: GOLB has four eyes and Grob Gob Glob Grod has four faces.
- "GOLB" is an anagram of "Glob."
- GOLB has a number of blocks floating around it that look similar to those seen at the end of "The Lich" and "Finn the Human."
- GOLB is similar to several H. P. Lovecraft cosmic entities, most specifically Azathoth, the "blind idiot" god embodying chaos and the creator of the universe.
- GOLB is similar to the Zoroastrian anti-god Angra Mainyu in that he is a deity-like figure (as opposed to the Satan-like Lich) symbolizing evil and chaos as well as essentially idiotic. Both entities are curiously similar in that the protagonists retrieve loved ones from their bowels: in Zoroastrian myth, Jamshid inserts his fist in Angra Mainyu's anus to retrieve his brother while Jake takes advantage of "Time Adventure" to free Finn, Simon and Betty from GOLB's stomach.