'''Satan'''
* AntiHero: Type V.
* DeadpanSnarker
* EvenEvilHasStandards
* GreenEyedMonster: The Professor often notes (to the point of it being a catchphrase) that Satan torments humans because he wants to bring everyone down to his level- he hates himself and his situation and wants everyone to be as miserable as he is. For extra points, Satan is actually described as having green eyes.
* KaleidoscopeEyes: At one point when Satan is losing his temper, the Professor notes that his eyes have gone purple; then, a little later, [[BlackEyesOfEvil completely black]].
* KickTheSonOfABitch: Most of the punishment he inflicts upon Thomas would be disgusting, but given how Thomas is a monster it's hilarious. Case in point: trapping him under an incontinent hippo for most of an episode before he eventually removes it... [[CrowningMomentOfFunny only to dump an incontinent and heavier rhino in its place]]. The rhino then tramples him before it goes off.
* LouisCypher: We always know who he is, we just don't know who he's pretending to be.
* NobleDemon
* PaperThinDisguise: He may be able to change his shape, but humorously, doesn't do much (or often anything) to change his voice.
* PayEvilUntoEvil
* PetTheDog: Every now and then.
* {{Satan}}
* WouldntHurtAChild: Satan has strict standards of not possessing anyone who isn't old enough to make moral choices, and is thus in one episode is shown to be [[EvenEvilHasStandards enraged]] at fundamentalists who believe a child is possessed by him, and want to beat Satan out of the child.

'''Thomas'''
* TheAtoner: Averted. The Professor, and then Scumspawn, spends a lot of time trying to reform Thomas. He doesn't really get it.
* ButtMonkey: Satan's personal punching bag, particularly because [[EvenEvilHasStandards Thomas disgusts even him]].
* TheCasanova: In life, he was pretty successful at seducing women.
* CorruptCorporateExecutive: Was one when alive.
* EvilRedhead: Stated to be red-headed in series six.
* FauxAffablyEvil: Thomas is [[Series/TheNewStatesman Alan B'stard]] on steroids.
* {{Flanderization}}: To an extent. In the first series, he's more of a malevolent cad, but later episodes present him as a rage-filled psychopath. Weirdly, this happens at the same time as efforts are made to reform him.
* PetTheDog: [[spoiler: literally, in season 7]].
* UpperClassTwit: A particularly malevolent one.
* AnythingThatMoves: Has sexual feelings for cartoon characters and mannequins. [[HaveIMentionedIAmHeterosexualToday As long as they're female, of course.]]


'''Gary'''
* ButtMonkey
* TheStarscream

'''Scumspawn'''
* AmbiguouslyGay: For Satan. He's a bad chooser.
* BumblingSidekick
* MinionWithAnFInEvil
* GeniusDitz: Arguably. He is a totally naive and incompetent, but is secretly an incredibly talented musician and artist. At one point, he is able to BUILD ROBOTS.
* ChasteHero: His love for his master is totally non-sexual. [[BarbieDollAnatomy Then again]], it kind of has to be.
* ExtremeDoormat: He once ate himself because Satan told him to.

'''The Professor'''
* FlatEarthAtheist
* MoralityPet: Essentially is this for Satan.
* WideEyedIdealist: His idealism is shattered only once during all seven seasons of torment. [[MomentOfAwesome He gets over it.]]
* StraightMan
* WorthyOpponent

'''God'''
* Jerkass
* AttentionWhore

'''Edith'''
* SuspiciouslySimilarSubstitute: [[spoiler: introduced after the Professor leaves and plays a similar role]]
* StraightMan
* CoolOldLady
* {{Determinator}}: As Satan notes 'arguing with her is like... well it's like cornering a badger'.