Fridge Brilliance: Otto's presence at the eating competition of "Around the World in 180 Bites" is a joke on his drug usage, particularly how smoking pot gives one the "munchies".
Fridge Horror: Remember in the last cutscene where Bart threatens to toss God's memory card into the ocean far below? Note that it said "Planet Earth" on it. Had Bart actually done it, he might have unknowingly destroyed Earth and ended humanity as we know it.
Not really, he would just erase a savegame of a minigame of a game. Remember, God is a character in Ralph Wiggum's game, who in turn is a character in the player's game... cue Mind Screw
Fridge Horror and Fridge Brilliance here. In the final level up in heaven you Fight a myriad of people you've already fought before, as lampshaded by Comic Book Guy. Why? Because you already killed them before, and they're in heaven now.
Fridge Horror as you see those loggers walking around? So in taking down the factory, Lisa killed dozens of ordinary people. COULD be Fridge Brilliance: as the logger mentioned, his father and grandfather and great-grandfather were all loggers - maybe you were just taking down their Heaven-based ancestors?
Fridge Horror: On the other hand, seeing those loggers you might have killed in Heaven probably means that you've been killing innocent, well-intentioned people throughout the game.
Fridge Brilliance: Every Characters abilities are based on their personalities and lifestyles:
Homer is often is seen eating junk food and drinking beer, and is also the most effected as far as forms go in Treehouse of Horror. His powers involve eating tons of food and changing forms.
Bart is a trouble maker and has been known to be rather athletic for a kid his age. Bart's play-style involves a lot of platforming, climbing and flying around, and the only character to attack characters from a distance consistently.
Lisa is the smartest of the 4 and isn't very violent. Lisa has the most puzzle-heavy gameplay and her Saxophone eventually makes enemies fight each other and eventually can use "Buda hand" to attack enemies as opposed to attacking them herself.
Marge is extremely naggy, but also very persuasive, and is (usually) a pacifist Her gameplay involves rallying up random people and is the least likely to fight.
Fridge Brilliance: Even if you ignore the Manuel, you're still unwittingly reading it! Why? It's part of the game's universe and it's how the family learns about their powers, so every tutorial is from the manual.