There's a whole conversation about which member ofthe Fellowship everyone is. While we didn't hear the final decision for everyone, we do know that Thomas is Legolas by virtue of prettiness, Sanya the sword-wielding descendant of kings is clearly Aragorn, Mouse is Gimli (shortest, stoutest, and hairiest), and, much to Harry's annoyance, the Leanansidhe got to be Gandalf (Best spellcaster in the group, and appropriately ancient and inhuman). Harry, they decided, is Sam: things rarely go his way, but he never gives up, and he's the real hero of the story. Oh, and Thomas labels Martin— the well-intentioned traitor who dies for their cause— as Boromir. And lo, there was Fridge Brilliance.
This leaves Frodo, Merry, and Pippin unassigned to Molly, Murphy and Susan for fans to argue about, which they've been doing non-stop since this novel hit the shelves.
There's also the obligatory description of the Black Council as "mysterious figures in black robes with delusions of Ringwraith-hood".
Harry asks Susan if she liked "those movies" too, when they're confronted by a huge roomful of goblins.
On a similar note, Harry compares some of his associates to the quartet from The Wizard of Oz. He pegs himself as the Scarecrow due to chronic bone-headedness, Thomas as the Tin Man due to how his skin looks when he's vamping out, Rudolph as the Cowardly Lion for freaking out during the Reds' attack, and Murphy as Dorothy by default.
Esteban's black silk clothing looks like something from a Hamlet dress rehearsal.
Harry having a flash of insight and asking Bob what the flowers in Lea's garden are only to be informed he took the primrose path. Hamlet is one of the earliest appearances of that phrase and Harry's talking to a skull.
When Harry decides to throw some wrath at some deserving vampires, he subverts the usual Gandalf quote about angry wizards:
Left outside while Susan and Martin raid Datasafe's computers, Harry grouses that he's Clifford the Big Red Dog: too big and dumb to accompany Emily Elizabeth indoors.
There's a passing mention of Loki in the Erlking scenes.
Harry's remark that he'd rather have a home that means something because of the ancient burial ground under the swimming pool could be a Poltergeist reference, although the cemetery under the Freelings' pool wasn't an ancient one.
Tilly checks his ID to see if the name has changed to "Mulder" when Dresden and Murphy start to level with him about what's going on. Harry himself conflates Tilly's appearance with Mulder's when he creates illusions of his companions.
Lea asks Harry if he's ever wondered why no enemy has ever sent spirits into his apartment by opening a gateway from the Nevernever, and lists his refrigerator among the possible destinations to which such a portal might've been opened.