"In a Moment's Time" is a sweet jazz song that initially sounds romantic. Paying closer attention to what the lyrics are implying reveals that the song is actually sung from the Skullheart's perspective.
Robo Fortune fires missiles that have mouse ears. What's another word for a missile? A rocket. What sound does a mouse make in Japanese? Chu. In other words, she fires Chu Chu Rockets!
Marie rarely flinches to anything but to the most relentless of Blockbusters or combos. During the introduction to Peacock's story, Dr. Avian gives some insight to her weaponry, describing the Z-Rays as being to able to 'disrupt a Skullgirl's very essence'. Coincidentally, Argus Agony happens to be one of the best Blockbusters when it comes to stun locking Marie. It's also very safe in comparison to most Blockbusters, and can hit Marie and destroy most of her undead servants simultaneously.
When Marie says that Umbrella 'reminds me of an old friend', it could be seen as Marie referring to Peacock - or it could be the Skullheart speaking through her, referring to Parasoul's mother.
In The Stinger of Robo Fortune's Story Mode she notes a "rising in sodium chlorine levels" when other characters attempt to fight back against her robot uprising. Basically she's calling them salty.
Why would the game be called Skullgirls if there's only one Skullgirl in the game, and she isn't a playable character? Fridge Brilliance kicks in when you realize that almost every single playable character in the game is a potential Skullgirl due to their wishes being considered "impure" by the Skullheart'sstandards.
What's the best way to make use of Ms. Fortune's Feral Edge Blockbuster? TigerKnee the motion.
Marie wearing a Maid outfit, right? What do maids usually do? Clean. What was Marie's wish? To clean up the streets, by getting rid of the Medici's!
Moreover, Fortune was granted the Life Gem's powers by swallowing it. Which is what Double has done, consequently. Good luck, anyone brave enough to fight a Double who can now regenerate near instantaneously...
In terms of Double's ending and her goals as seen in Beowulf's story, She intends to eat everyone who gets in her way or fails to make a wish, and seemingly is absorbing them into herself. This is likely why she can shapeshift into other characters and use their moves and abilities. She's absorbed the fighting prowess and abilities from all the playable characters from every possible bad-end, then moves to the next one. A horrifying abomination that not only has all your strengths but knows she can beat you because she already has!
Eliza doesn't actually have a body anything on her that isn't Sekhmet is basically blood. Including her skin, clothes, face, everything.
It's implied that when Squigly first got Leviathan she had to help put down her Skullgirl mother. On her mother's birthday. Yeesh.
Even more for Squigly, since her fate is horrible. Squigly is trapped in a never-ending loop of violence now. Whenever a new Skullgirl arises, the dead and Squigly rise again, but due to Leviathan she is immune to the Skullgirl's control. Meaning that she must defeat the Skullgirl if she ever wants to rest, but the Skullheart is guaranteed to appear again every 7 years, so it will inevitably awaken her once more and repeat the process forever. And just to make things worse, Squigly's body will continue to degrade over the years until all that is left is a skeleton. There is some solace in that Squigly is the perfect counter to the Skullgirl, and as long as humanity and the Skullheart exists so will Squigly and Leviathan to stop them, though this is a cruel fate to bestow upon a 14 year-old girl who would probably never want this kind of fate.
When Peacock arrives in Lorenzo Medici's office at the end of her story mode, it's implied that she got there by killing all of the Medici goons that stood in her way. Which quite probably includes Cerebella. In fact there's actually supporting evidence for this - in the shot with Peacock and all her cronies in the ending, she's holding a tattered scrap of Vice-Versa in her hand.
When you play through the story modes for Double and Eliza, you realise something horrible about The Trinity: The revered goddesses of this world are actually former mortals who somehow ascended to godhood centuries ago, and at least one of them was killed by Eliza. Because of this, they hate humanity and want to destroy them; they created the Skullheart and its Skullgirls in hopes of eventually wiping humanity out. Oh, and the Skullheart? Is actually the last mortal remains of "The Mother". So, without even knowing it, humanity is worshiping a set of Eldritch Abominations who actively want to kill them all! Talk about Villain with Good Publicity...
How about this: Cerebella is stated as being so "pure at heart" that she could have actually wished on the Skullheart without becoming a Skullgirl. That's right, the girl who crushes Ms Fortune to death for a mobster is somehow purer than Filia or Parasol.
Is it worse that she can do what she did in her ending and still be somehow better than the entire cast, or is it because she's the only selfless woman on the whole planet that could potentially end the Skullheart, but is hopelessly devoted to a monster?
Or is the "pure-hearted" thing because she never actually tries to wish on it? (Given that the purpose of the Skullheart is to create Skullgirls...)
Extending from the question of whether Skullgirls is eligible for the Grand Unified Timeline (answer: probably not) - judging by the trees in Maplecrest, the game takes place in early autumn. That probably means that Peacock's birthday (November 13th) is coming up. Happy birthday, Peacock - you have to kill your best friend.