TLDR: Are ghosts actually real in Bones and is there any Word of God evidence to support this? Does that mean Teddy was really there, and not just a hallucination?
I am watching Bones and have just finished seeing Season 4 Episode 13- "The Hero in the Hold". The plot revolves around resolving the Gravedigger plot thread from Season 1. Booth was kidnapped by the Gravedigger, and put on a boat slated to be sunk. Booth seems to experience a hallucination due to possibly being drugged or a concussion or trauma from a cattle prod. The hallucination, Corporal Edward "Teddy" Parker, seems to help Booth escape throughout the ship. At the end, he disappears, only to appear at the epilogue.
Of course, the episode is vague about whether Teddy is actually there or not. Typically when someone Hallucinates another person, said hallucinations actions are either just a projection that doesn't affect the surroundings, or their actions are actually performed by others, only attributed to the hallucination (Fight Club style). It could simply have been Booth doing everything, talking to himself. Yet, Dr. Brendon points out that it would have taken two people to do some of those things. And in the epilogue, Teddy appears to talk to Dr. Brendon, and she responds!
Assuming that the episode was meant to be vague and leave ghosts as "maybe possible" without any proof, a typical "Is it real or not" episode for the audience to ponder, recently Bones had a crossover with Sleepy Hollow, a show where Ghosts, Demons, and other supernatural elements are 100% real and canon. While both have the Buddy Cop genre in common, Bones is firmly rooted in science fact while Sleepy Hollow in horror fiction. Besides being a marketing ploy, this implies that they share a common universe, so my question being the TLDR at the top, are the ghosts real in Bones.