Father Callahan (first appeared in Salem's Lot)

Father Callahan is mentioned in the following books:

The Dark Tower V: Wolves of the Calla (Nov 2003)

Boom. Callahan is back.

Telford recovered himself with relative speed, but when he spoke, Tian thought he still looked shocked. “Beg pardon, Pere Callahan, but I have the feather—”
- Prologue / Section 3

The Dark Tower VI: Song of Susannah (Jun 2004)

Father Callahan plays a large part in this book, but the strangest moment is when he and some of the other characters find a copy of Salem's Lot in the Manhattan Restaurant of the Mind (the Stephen King book where Callahan first appeared).

Father Callahan took a cup of coffee with a nod and a distracted smile, but no word of thanks. He had spoken little since they’d come back from the cave. In his lap was a book called ’Salem’s Lot, by a man of whom he had never heard. It purported to be a work of fiction, but he, Donald Callahan, was in it. He had lived in the town of which it told, had taken part in the events it recounted. He had looked on the back and on the rear flap for the author’s photograph, queerly certain that he would see a version of his own face looking back at him (the way he’d looked in 1975, when these events had taken place, most likely), but there had been no picture, just a note about the book’s writer that told very little. He lived in the state of Maine. He was married. He’d written one previous book, quite well reviewed, if you believed the quotations on the back.
- 1st Stanza / Chapter 1

Roadwork (Mar 1981)

Phil Drake, the man who was once a priest but is no longer one bears a striking resemblance to Callahan. He makes a point of not wanting to be called "Father", he's an ex-alcoholic, he has an oddly scarred hand, etc.

“You're a minister?"     "They call me a street priest. Very romantic. Malcolm Boyd, look out. At one time I was a real priest."     "Not any more?"     "I have left the mother church," Drake said. He said it softly, but there was a kind of dreadful finality in his words. He could almost hear the clang of iron doors slammed shut forever.    "Why did you do that?"     Drake shrugged. "It doesn't matter. What about you? How did you get the mesc?"     "I got it from a girl on her way to Las Vegas. A nice girl, I think. She called me on Christmas Day."     "For help?"     "I think so."     "Did you help her?"     "I don't know. " He smiled craftily. "Father, tell me about my immortal soul. "     Drake twitched. "I'm not your father.”
- Part 2 / December 31, 1973