Pain and Panic are two shape-shifting imps who are minions of Hades and the Hellfire Organization in the Kingdom Hearts Unlimited Saga, first appearing in "The Journey" as minor antagonists for the Mt. Olympus campaign. Neither are very intelligent or especially loyal to him, and serve Hades only because they fear him and possibly because he owns their souls.
Hades uses them as pawns in his schemes, and during the movie, they are also used by him to keep an eye on Megara, shifting into bunnies, chipmunks and birds to do so, and when he loses his temper, occasionally as punching bags.
According to mythology, Pain and Panic were formed during the Lands of Legend by Lord Cronus using the hellish energies of Tartarus during the last days of the Titanomachy as two of many Misery Imps to serve as the embodiments of all the sins and miseries of Mankind. Under the Titans' orders, Pain and Panic joined their compatriots in tormenting the humans who dared oppose their regime. When the God Pantheons united to take down the Old Ones' regime, they were able to defeat their chaotic predecessors and their Misery minions by sealing them in two magic boxes known as the Seals of Pandora. However, Pandora, the immortal demigoddess assigned to watch over the boxes, got curious about her role in Fate and ended up releasing the Old Ones from one of the boxes during what is now called the First Pandora cycle, an event occurring during the time of the LoL. The Miseries were freed from their own box many centuries later in the second Pandora Cycle in our Modern Era when Pandora was tricked by Hades into doing so in order to recruit the Miseries as his new minions. They only remained free for a short time before Pandora was able to seal them back in their prison, leaving only Pain and Panic behind by accident. Nonetheless, Hades was able to enslave the two Miseries as his personal henchmen by sheer force of authority, and assign them to watch over the Underworld as security of a sort. Their relative freshness in existing in evident as they are the newest imps to take on the Misery titles following their Old One predecessors, which explains how Discord, an Ancient One who frequently collaborated with the Titanomachy rulers, never knew about the two imps when he last visited the Underworld during the last few aeons of the Age of Chaos before returning a second time in the Modern Age.
Pain is the shorter, wider of the two, and is a pink-skinned imp with a large mouth filled with sharp teeth. He has spindly arms that end in four-fingered hands, while his legs are much stockier and end in two-toed feet. His wings, which have purple membranes, seem too small to actually fly with. Pain's hair is maroon and styled into two horns, with his real, black horns sprouting out just behind, and his pointed tail is the same color as his hair. His nose is very small and a darker shade of pink than the rest of his skin. His yellow eyes are set very close together, he has a thin, black uni-brow, and his upper eyelids are a dark purple color.
Panic is a blue imp and much thinner and taller than his partner. Panic's arms, though just as thin as Pain's, are much longer, as are his legs, which end in two-toed feet like Pain, albeit Panic's feet have navy toenails. His eyes are the same yellow color as Pain's, but his are much larger and even closer together than Pain's. His lower eyelids are a darker shade of blue than the rest of his body, and his nose is enormous and pointed, with prominent nostrils, sharply contrasting with Pain. Panic does not have hair like his friend, and instead has much larger horns that are the same color as his skin, unlike Pain's black ones. Panic has the same small, seemingly useless wings as Pain, with navy blue membranes, and his pointed tail is also navy blue. Finally, Panic's teeth are very even and straight, as opposed to Pain's jagged, pointed ones.
Pain is the fat pink/purple imp with little horns and a bitten bat wing on the left side. He is repeatedly injured through the film and animated series. When he shape-shifts, it is usually into something short or fat (or both), and generally coloured in red tones. He is the more assertive of the duo, and while more cunning, less likely to think things through properly, which is what gets him into painful situations.
Panic is the thin blue/green imp with long horns. While he is slightly less cunning than Pain, his paranoia means he is very much more cautious and rather cynical at times, so he might actually be the smarter one of the two. However he is easily spooked, which causes accidents and messes up plans. When he shape-shifts, it is usually into something tall or thin (or both) and coloured in blue tones.
They appear to be immortal and capable of regeneration, but being demonic rather than godly, both are capable of feeling pain.
Their shape-shifting abilities extend to being capable of shifting only part of their bodies, shifting into shapes both larger and smaller than they themselves are, and even more importantly, merging into a single form; however this seems to be a more temporary and harder-to-control ability. Their shifting abilities do not seem to extend to voice-mimicking, and they have to do the best they can with their own voices.