The final episode.
Kolchak is related to The X-Files' Arthur Dales
Kolchak's hat is an ancient artifact granting ultimate power.
Kolchak is either psychic or some form of monster himself.Despite being given the barest of clues and never exhibiting great detection skills,Karl Kolchak manages to locate and defeat monsters in a crowded urban area with little or no assistance. These monsters included an alien, a humanoid, and TWO separate vampires. How could this be possible? Either Kolchak SENSED the presence of these creatures, or he was a creature himself and had an affinity.
Kolchak is responsible for Special InvestigationsWho else would cause the police so much trouble that they're forced to create a special division in the department to explain everything away, and so understaffed that it could do little.
The series takes place in the same universe as The Rockford FilesThe final episode of Rockford had Jim meet a reporter with the Independent New Service, the same news service Carl works for. One of the writers of the episode was Rudolph Borchert who wrote several episodes of Kolchak. The shows shared more than one creative personnel. David Chase (later of The Sopranos) also worked on both shows. Simon Oakland (who played Kolchak's boss) appeared in a few roles on Rockford.
Kolchak's tapes still existThey were picked up by Harry Dresden, giving him his first encounter with the supernatural. (Why Dresden? They both live in Chicago.)
Kolchak is delusionalI know it's a Stock Epileptic Tree, but hear me out. Kolchak always goes in with a preconceived notion about what the supernatural menace is, and of course he turns out to be right... from his perspective. Nobody ever corroborates his story even if they (according to what Kolchak remembers) saw it too, and at the end of every episode all the evidence is always mysteriously destroyed. He clearly remembers something supernatural happening, but neither other witnesses nor the physical evidence can back him up on that. Everyone he knows very clearly expresses the fact that they think he's insane, but we the viewers know he isn't and that they're just Jerk Asses because we saw the monsters too. But then, the show is told entirely from Kolchak's perspective, with articles written by Kolchak about what he remembers seeing as the Framing Device. We're just seeing what Kolchak remembers seeing, whether or not it was ever actually there.