Ruby Gloom/WMG

Misery is a banshee.
This is implied in the show, even if it's not official. She a harbinger of disaster, she wails when she tries to sing, and she's doesn't look entirely human. Also, you only ever see her female relatives (It's a well known fact that banshees are always female), and they are all remarkably similar to her. This is bacause banshee genetics are different. Banshees procreate by mating with males of other hominid species - Often humans, but also fairies, elves, or even vampires - but their offspring will always be daughters, and always banshees.

The inhabitants of the house are all adults.
They're proportioned exactly the same as the other adults on the show, and Misery has cousins who are quite obviously children. Frank and Len have several tattoos. This also solves the question, "How do these 6 kids own this massive plot of land?"

Banshees are immortal.
This is the reason why Misery survives, and quickly heals, from any accident that happens to her. This is also why she acts so calmly even when she thinks something is going to end with a disaster - she knows that she'll survive it. However, she often worries that her friends will get killed; that's why she is sad so often. Further proof: During a family reunion we are introduced to Mayhem, a relative who is old enough to remember the dinosaurs. Granted, that whole family reunion might have been a dream, but prior to that, she speaks of Mayhem as if she was still alive. She speaks the same way of Migraine, a relative who was aboard the Titanic. In another episode, Misery looks exactly the same in a flashback from seven years ago. Furthermore, Misery owns the key to the lost city of Atlantis and it was given to her by her great-great-great grandmother (personally), who got it from her great-great-great-aunt (personally), who won it in the Atlantis bake coven - You do the math.
 * Plus, even if it was a dream, Misery's line about the family reunions only happening once a millenia and that she'll see them at the next one...

Misery and her family are an alternate universe equivlent to The Endless.
A family of powerful beings with Perky Goth designs that are personifcations of abstract concepts that all start with the same letter. Never Heard That One Before.

The series is set in the same world as either Corpse Bride or the cartoon Beetlejuice--or both!
This would explain why the characters never age, why there's skeletons running around (maybe Skelly-T, Jacques and Bonejangles are related!) and why a bunch of kids own a large ammount of land-since they're dead, who says they can't? Heck, maybe Bonejangles or Jacques owns the house and just lets them live there, explaining why Skelly-T pops up so often and takes such an interest in Skullboy! OH MY GOD, IT ALL MAKES SENSE!!!!

...I smell fanfiction...

Assuming he ever was fleshy, Skull Boy used to be African-American or black british.
He just really seems like an extra-geeky, extra-square black kid character, and in the episode with the N'Awlins themed skeleton music club, he finally manages to pull of being hip and it's in that was that only Joe Cocker, pimps, or both can look even remotely natural when doing while white. This also adds highly interesting (but not necessarily truly unfortunate) Unfortunate Implications to some of the things he thinks his ancestors are/did (such as traveling to and exploring new places without being involved in the actual navigation, or descended from Shakespeare).

It's all in her head
Ruby is a mental hospital patient, and she hallucinates a whole world. The "bright side of the dark side" is not the sweet side of monsters, but rather the happiness experienced during insanity.

The show will be Un Cancelled and will return with a third season
It will also FINALLY air in the United States. Which channel the show will broadcast on is open to speculation.
 * Y'know, I actually wanna see a third season of Ruby Gloom sooo bad.