He is a human social services coordinator at the Department of Integration's Social Services Department in Manhattan. He holds regular sessions to help the new immigrants adapt to life in New York. The sessions are collectively referred as "Mark's class". Even though he may have only the noblest intentions in heart, he often fails at helping the immigrants deal with their personal problems and integrate in society due to careless or clumsy mistakes. He seems to have at least some kind of basic education in psychology, often taking a diplomatic, empathetic approach to others' problems.
He is also the chief operating officer at the Department of Robotic/Android Rehabilitation which he is not aware of until Francis Grimes brings him the robot J9. It was Leonard Powers who signed him up for the job mistaking that for joining the softball team, as told in the episode "Soul Sucker".
He is shown to be quite intelligent, as he was able to make plans that go exactly the way he wanted or expected to happen, such as making a clone of himself to fight Twayne Boneraper in "Hell for the Holidays", knowing full well that Twayne will double-cross him on their agreement for not killing him. This caused Callie to remark on his survival instincts in an admiring tone. Mark showed a strategic side again in "Wail Street", where he is able to not only get the Maggotbones to stop trying to steal his soul, but even make a hefty profit in doing so.
He is Callie Maggotbone's boyfriend and friends with zombie Randall and wizard Leonard. He does not get along well with Callie's father Aldermach. He works at the DOI where he often comes into conflict with the anti-immigrant Grimes during the course of his attempts to help the immigrants in need. Twayne from time to time relies on Mark for work-related subjects and personal matters.
Mark used to have a girlfriend in college called Jaclyn Anderson, as told in "Lilly and the Beast". They meet again in Mark's class after she has been caught for vagrancy. They almost rekindle their feeling for each other.
By the end of the second season, Mark is "engaged to be engaged" to Callie.
Mark Lilly's mother is first seen in "Trolling for Terror". She has similar features as Mark, with brown hair and pale skin. She seems to have got intimate with Clark Dungaree in the episode. Mark has a dream of his mother in crotchless panties in an orgy in "Soul Sucker".
Mark has not seen his father since he was five. His mother says that his father is still stuck in traffic, as he reveals in "Ride Me to Hell".
It is revealed in "Fools for Love" that he had a stepfather who loved pranks. He walked out on Mark on April Fools' Day right after screaming he wished he had not met Mark's mother when Mark was twelve.
In "The Ring of Powers", Mark tries on Leonard's engagement ring and takes his place to marry the wizard princess Beatrice, the heiress to the Bedfellow throne, which is also the Mattress King and Queen of New York. She becomes an insentient zombie right after emerging from the ice. She is crushed to death on her wedding day by the elevated viewing stand wrecked by Doug's rifle shot. Since Mark is in her will, he will never need to buy a new mattress again.
- Lesbian Hair: The chief of a bacterial village inside Twayne's body calls Mark by the name "Lesbian Hair" in "Journey to the Center of Twayne".
- Rick Nightingale: Mark takes on a new stage persona in "The Roast of Twayne the Boneraper".
- Batperson: After getting bitten by a rabid bat boy, Mark dons a mask and a costume, and begins to fight crime as the vigilante "Batperson", in "The Dork Knight".
- It is unknown exactly how tall Mark is, but most of the time he is shown to be a bit taller than Grimes who is 6'2".
- Mark has night blindness, as told in "Fools for Love".
- His left big toe gets eaten by Randall after his death in "An American Werewolf in America" when Randall does not know that he is going to come back to life. However, by the episode "Treegasm", he has his toe back when he is seen running out of the toilet booth during the treegasm event.
- Mark is an inveterate punster, often making puns that no one else thinks are funny (leading him to command people to laugh at them in the episode "The Ring of Powers").
- Mark has a personal rule against swearing (leading to his many odd exclamations), which carries over to Clone Mark in "Attack of Mark's Clone", leading Callie to remark that it must be "in his DNA".
- It is clear he wishes to have a family with two children, a son named Ethan and a daughter named Desiree. ("Wail Street")
- Mark has cheated death three times. First in "An American Werewolf in America" Leonard has granted him immortality for a dangerous stage performance. A second time he falls to his death, after which Leonard simply rewinds the last milliseconds of his fall. And a last time in "Hell for the Holidays", Mark creates a clone of himself to die in a battle to the death with Twayne in Hell.
- Mark's favorite food is eggs, including his own invented dish, the Egg Dog (simply eggs and bacon in a hot dog bun) ("Better Off Undead"). He is also fond of the "Egg-cano" (a large mountain of eggs which Randall liberally squirts with hot sauce) ("Mummy Dearest"). He has a subscription to the Oeuf magazine ("Soul Sucker").
- Mark enjoys pepper on his food. He often asks for additional pepper after tasting a meal.
- Mark has a movie blog. He scores movies by "marks", for a maximum number of five. ("Fools for Love")
Even though Mark is a social worker, he has caused death to others from time to time.
- A manbird: Mark fires his gun to the sky to interrupt Phil and Matthew from arguing. But the shot hits a manbird which falls down and bounces off a car roof. ("An American Werewolf in America")
- HIMSELF: Leonard performs at Open Mic Night and tries to do a magic of bringing a dead person back to life. He persuades Mark to shoot himself. As Leonard has earlier gifted Mark with "One Day of Immortality", Mark is brought back to life, not immediately at the show, but much later at his own funeral. ("An American Werewolf in America")
- Rico Rodriguez: Mark misfires his gun and kills Rico during his temporary employment as a member of the goon squad. ("Any Given Workday")
- A number of Tiny Leonards: Mark needs to kill all but one tiny Leonards so that the remaining one will become Leonard again. First he lets many of them die due to his negligence. Later he hired Grimes to kill the rest. ("Kill, Mark... Kill!")
- His own clone: Mark creates a clone of himself to take his place in the blood courts in Hell and get killed by Twayne. ("Hell for the Holidays")
- A woman dancing outside his apartment: Mark uses the "power of influence" from Leonard's magical wedding ring and orders the people outside his apartment to dance. When Randall reminds him there are people dancing outside for 10 hours, he hurriedly stop them, but at least one woman has danced herself to death. ("The Ring of Powers")
|Series and Games||Ugly Americans ‧ 5 On ‧ FUGLY | Citizen Ugly ‧ Apocalypsegeddon|
|Characters||Main||Mark Lilly ‧ Randall Skeffington ‧ Callie Maggotbone ‧ Leonard Powers ‧ Twayne Boneraper ‧ Francis Grimes|
|Recurring|| Aldermach Maggotbone ‧ Rosie ‧ Melchior ‧ Goon squad |
Mark's class : Croatian Man ‧ Doug ‧ Erik ‧ Great Brain ‧ Martin ‧ Toby
|Matt Oberg ‧ Kurt Metzger ‧ Natasha Leggero ‧ Randy Pearlstein ‧ M.L. Wooley ‧ Larry Murphy ‧ Julie Klausner ‧ Devin Clark ‧ Pete Holmes ‧ Mike O'Gorman|
|Writers||Devin Clark (creator) ‧ David M. Stern (development) ‧ Daniel Powell (exec. producer) ‧ Greg White ‧ Bill Krebs ‧ Jeff Poliquin ‧ Aaron Blitzstein ‧ Nate Federman ‧ Kevin Shinick|
|Directors||Devin Clark ‧ Aaron Augenblick (supervising producer) ‧ Richard Ferguson-Hull|
|Species (list)||Demon ‧ Human ‧ Manbird ‧ Succubus ‧ Vampire ‧ Wizard ‧ Zombie|
|Other categories||Episodes (list) | Government ‧ Items ‧ Locations ‧ Magic ‧ Media|