Bugbear is a type of Hobgoblin that is comparable to Boogeyman and Bugaboo in folklore. Bugbear was used to frighten children into obeying their parents. Its name is derived from the Celtic word bug which means "evil spirit" or "goblin." In lore, the Bugbear was depicted as a creepy bear that lurked in the woods to scare children.
"A Welsh creature commonly known as "Bugbear" or the "Boogeyman". Its existence is often used by mothers to scare children into behaving."
—Persona 5 background
The Shadow of Yumeko Mogami takes the form of Bugs when confronted in Mementos during the request The Lovesick Cyberstalking Girl. During the battle, she lacks the weakness to Nuclear skills and has additional skills such as Marakunda, Brainshake and Stagnant Air. Defeating Shadow Mogami will yield the Sticky Hairball key item, which allows Bugs to be fused through an advanced fusion of Pixie, Pisaca and Hariti once the protagonist reaches level 49.
Bugs is subject of one of Caroline and Justine's requests, needed to advance the StrengthConfidant to rank 9. They wish to see Bugs with the Samarecarm skill. This can be accompolished by leveling Hariti to level 41 before fusing Bugs, allowing her to simply pass on the skill during advanced fusion.
Bugs is also one of the Personas used by Justine in the optional boss fight against the Velvet Room attendants.