Bugaboo is another name for the Boogeyman. It is an evil or mischievous spirit. It is similar to the Bugbear. It is a fairy said to inhabit mines and coastal areas as a Hobgoblin during storms. It is associated with the Pooka.
"Elements of the earth inhabiting the Cornwall region of England, akin to goblins. They are pranksters, but also possess a more fearsome side, attacking and eating humans. Bucca-Boos were also sometimes seen as water sprites. When fishermen were blessed with a good catch, they would give offerings of fish and ale to the Bucca-Boos in hopes that their next catch would be good as well. There are two types of Bucca-Boos. White ones are good, while black ones are evil."
An important character who represents the Chaos alignment, he's an odd demon found in Mitra's laboratories in Sector Bootes, Bugaboo stands above common demons for his unusual genetic composition: he is not a pureblood demon, but rather, only has 75% demon genetic material, which makes him virtually unique among the Schwarzwelt denizens. He also comes in two variations, Bagaboo and Bogaboo, of the Law and Neutral alignments, respectively. It is heavily implied Bugaboo was created with human genetic material for experimentation purposes.
Bugaboo is found being tortured by fellow demons; after Jimenez saves him from said demons, Bugaboo bonds with him and partners up with him. Bugaboo initially speaks in a simple manner, only being able to say either his name or Jimenez's. Jimenez takes a liking to Bugaboo and treats him like a friend throughout the story, prompting Jimenez to disobey rules regarding demon handling aboard the Red Sprite. In turn Bugaboo becomes very loyal to Jimenez, even willing to take a shot from the protagonist's MK Gun while Jimenez is still brainwashed.
In Sector Carina, Bugaboo furiously attempts to charge against Horkos, who at the time was still holed within the Elve after he attacked Jimenez. However, due to the Elves plasma armor, Bugaboo was swiftly destroyed and absorbed by Horkos' armor. Later on, after banishing Horkos from the ship, Jimenez found Bugaboo's forma and re-summoned him with the Compendium information stored in his Demonica. Though he was slightly annoyed he had to teach Bugaboo to speak English again, Jimenez gladly took it in stride, just happy to have his friend back.
While spying on Jack's Squad with Jimenez, Bugaboo is said to have entered into their base. Although it is never stated why, it is likely Bugaboo did this because of the experiments Jack's crew was doing to demons at the time. After Jimenez caught up with Bugaboo and proceeded to damage a lot of experimental equipment, disgusted by the inhuman treatment of the demons, the two were captured by Jack's Squad and sent to be experimented on.
Shortly afterwords, the protagonist came and saves the pair from Jack's technicians, though the scientist carrying out the experiment engaged the crew's heavily flawed fusion machine on the two. Due to the injuries sustained from the experiment, Bugaboo was dying, causing Jimenez to plead with the protagonist to fuse him with Bugaboo through the Demon Fusion Program in order for Bugaboo to live on through him. Regardless of the protagonist's choice, Jimenez will fuse himself with Bugaboo, causing Jimenez to obtain his Awaken form.