Character Analysis
Like most fairy godmothers, this character is sort a huge question mark. All we really know about him is that nobody knows about him or his connection to Campbell:
My lawyer here in Jerusalem, Mr. Alvin Dobrowitz, has told me that I would surely win my case if I could produce one witness who had seen me in the company of the man known to me as Colonel Frank Wirtanen. (32.1)
We do eventually get some proof—and we use this term loosely—of Wirtanen's identity when he writes a letter saving the day at the end of the novel. You know, it's one of those letters: "It's me! By the way, here's my real name and ID. All clear now. Go home. Nothing to see here." It's super convenient that this mystery dude who pops up like a nanny with a flying umbrella out of nowhere fixes everything in the eleventh hour.
Let's clear one thing up, though: magical this dude is not. He does have an uncanny knack for showing up whenever Campbell needs to get out of a sticky situation, but that's just because he's like one of those weird characters on the X-Files who is so deep into the international conspiracy that he knows everything about everything going on, all the time.
P.S. This isn't the only time Vonnegut uses the Blue Fairy Godmother moniker for one of his characters.