Sterate Baboogeddon/WMG

Dr Zoom has a grudge/obsession with Felincia.
Why else would he almost have his men rape her? He has to have some bone to pick.

Jolly Roger should be fucking arrested for giving two 15 year olds alcohol.
In book 1, we find Ginger Beer as an innocent drink Jolly proudly serves. In book 2, Banjo and Bottles get drunk from it and begin playing strip poker. Unless those were virgin Ginger beers he served Daniel and Andres, Jolly should hide from Hyperian police.

Daniel or another character will end up fighting Cailou and his dad.
In the beggining of book 2, Cailleta references that she killed Rosie (Her own daughter), but Cailou and Cailleta's husband are still alive. Daniel, Felincia, or another character might challenge Cailou or.... Cailloto to a duel. The highest probability of this happening is at the final book.

The Shadow Beings are The Heartless.
Think about it, they reside at the core of every universe, they are black with gleaming, vacant eyes, and they attack in large numbers. Sounds like the Heartless to me.

Daniel hates his life on earth.
His argument with Andres and refusal to go home in book 2, leads this troper to believe Daniel might've thought up Hyperion to dwell on it as shelter from his crappy reality. He seems way too into the fun events he partakes in at Hyperion, and rarely gives any mention of his family back on earth unless told about them. Fantastic misanthropy, anyone?

Haruhi Suzumiya. Haruhi was bored, so she decided to fire up her spaceship and travel the universe, searching for ideas to make more universes. One day she orbited around earth and used a ship sonar to overhear Daniel and Andres talking about how great it would be if their was a universe where all videogame characters can live in peace. You know what happens next.