It’s not like this is the only time something like this has ever happened, you know.

There’s also Clara’s job, that changed when Moffat wanted a cameo from Coal Hill School in the 50th.

Amy’s job just changed on a whim when Moffat felt like changing it. Starts as a kissogram, then becomes a model, then when she goes back in time suddenly she’s writing children’s books (although that’s only mentioned in an unfilmed minisode).

Characters do not exist to be characters, they exist to add cool things to the plot.

Clara’s job? The one that she had all throughout season 8? That’s something that was mention in one episode and then forgotten all about? 

As for Amy going from job to job, that sort of tells us a lot about her character and how much she hates being tied down. Also, she was shown throughout the series to be creative and imaginative, she made cartoons as a child, so her ending up as a children’s writer makes a lot of sense. 

And all characters exist to add something to the plot. That’s kind of the point of characters. 

In one of Clara’s first scenes (as herself, anyway, and not an echo) we see Mr. Maitland tell her that they’ve already put in the advertisement for a professional nanny, so we know right from the start that she’s going to get another job eventually.  Her teaching job is introduced in “Day of the Doctor” with very little effect on the plot, but it’s an actual plot point in “Deep Breath,” “The Caretaker,” “Kill the Moon,” and “Forest of the Night,” and it appears in even more episodes than that.  So it’s hardly something that exists for a cameo.

As for Amy, her job as a writer was established at the end of “The Angels Take Manhattan,” and the fact that she wrote young adults’ books was confirmed onscreen in “The Bells of St. John;” the book Clara and Angie were both reading was written by Amelia Williams (although I’ll admit it takes a sharp eye and probably a pause button to catch this one).  She had writing experience before that, though; she was writing travel articles in (I think) “The Power of Three.”  More than that, though, there’s a pattern to Amy’s jobs.  She invariably chooses something that’s fairly freeform, in which she would be largely in charge of schedule, and something related in some way to imagery.  (In case it’s not obvious, being a travel writer would depend on the ability to convey a tangible and appealing sense of place, a thing which relies extensively on sensory details, and that spills over into fiction writing.)  Her jobs can also be abandoned with minimal guilt; she isn’t responsible for anyone’s welfare in the way a nurse or even a teacher would be.

Granted, you can call it unrealistic that Amy apparently moved very quickly into big money modeling, with a personal signature line of perfume and, evidently, a favorable enough contract to name it after something relatively few people have ever heard of.  But the idea of Amy being a model is the exact opposite of farfetched, considering that was the way Karen Gillan put herself through school.  And nobody ever claimed that Amy was allergic to hard work; her problem is with commitment.

Amy’s writing career is in an unfilmed minisode?

It looked pretty filmed to me…