After reading this blog post about players who spent very little time with the Royals, it occurred to me that it is possible for a pitcher to be credited with having appeared in a major league baseball game even if he was immediately replaced before having thrown a single pitch. So, I was wondering: has there ever been anyone in major league history whose entire career is credited as having appeared in a game, but who never threw a pitch, wasn’t on the field for any time that the ball was in play?
Meet Larry Yount, Robins brother.
Thanks! I wonder if he’s the only one.
The position player equivalent to Larry’s story is Frank Verdi, who was announced as a pinch hitter, called back after a pitching change and never played in the majors again.
No, Verdi played the field, but was pinch-hit for when he came up to bat. I don’t know of any player besides Yount who fits the OP definition of not having been either (a) on the field, (b) at bat, or (c) running the bases at any time while the ball was in play.
While he doesn’t QUITE fit the bill I need to throw him out here:
Yes, he was real.
And, I’ll note, that for position players if they’re in the game they’re in the game whether they do anything or not. So someone who was called up but never hit the field or batted would not be credited with any game time.
So you’d want someone who was called up, placed on the line up card that was given to the umpire, then for any reason was pinch hit for in the first inning prior to coming up to bat. Hmm…it would have to be a visiting team, too.
That’s the only way I can see a position player getting credit for a game appearance but not batting or taking the field.
There’s Eddie Gaedel; one pinch-hit plate appearance, drew a walk (so, not an at-bat) on four straight pitches, replaced for a pinch runner, never played again.
Not your typical ballplayer.
Damn you, Robot Arm! You got here with him ten minutes before I did! 
Not quite the same thing, but there was a California/LosAngeles/Anaheim Angels pitcher a couple years back whose first professional at-bat (major or minor league) was in the World Series.
An even further stretch would be designated pinch runner Herb Washington- no at bats, never played the field.
The more common scenario would be that a player was announced as a pinch-hitter, but then taken down when the other side changed pitchers. (Such a player is credited with a game played.)
This happens fairly frequently–so much so, in fact, that it’s surprising that the only player (that we know of) with a “null” career is a pitcher. It’s more difficult for a pitcher to log a null game, because he must face one batter except in case of injury (the exception which applied to Yount).
No discussion of micro-careers would be complete without reference to Adam Greenberg, beaned in 2005 by the first pitch in his first (and so far only) major league plate appearance.
Granted, Walter Alston isn’t exactly what the OP is looking for, but I’m always amused at the major league playing record of this Hall of Famer*.
*As a manager, that is.
Like Freddy the Pig, I’m pretty sure that Larry Yount is the only one who fits precisely the OP’s definition.
As for microscopic careers, I’ll add to Adam Greenberg Fred Van Dusen, who as a Phillie in 1955 was also hit by a pitch in his first and only MLB at-bat ever. He never played the field.