Hallowe'en house

The faculty of Epistemological Eschatology had gathered together in the Common Room to look at the perspex display cases and what they contained.  As the faculty, on a good day, numbered only four people, there was no pushing or shoving, no peering over each others shoulders or standing on tiptoes, and very little in the way of awed conversation or startled comments.  Dr. Malmstein was tapping a pipe (that he never smoked) against his teeth, and Bob was wondering if it would be rude to sit down and stop gawking at the display cases.
"We were hoping you might have some insights," said a man of medium height.  He was wearing overalls and clutching a grey checkered flat cap in his hands.  There was a small amount of dried mud on his boots, and a faintly smoky smell about him.  His hair was sandy-coloured and just starting to turn grey at the fringe, and he looked earthy.  Bob thought he was highly suspicious.
"Well," said Dr. Malmstein, the pipe clinking gently against his teeth and muffling his voice, "I would say that you've got some skulls here.  Human by the looks of things.  You might want to check with the local council about the legitimacy of you keeping them you know."
"Yes, but what about what's been done with 'em?" said the man, his accent uniform across his words, not too thick to be hard to understand, but always there like it was important to him that you knew he had an accent.
"You mean the houses?"  Dr. Malmstein raised both eyebrows, one after the other like some bizarre mexican wave performed in miniature across his face.  The man nodded, and Bob decided at that moment that this was definitely a put-up job.
The tops of the skulls had been broken open and little houses, complete with gardens, had been constructed in the brain pan.  Tiny bricks had been mortared together painstakingly, and each house had at least three storeys.  One of the three even had flying buttresses and a little tower.  The windows were mostly left open, but a couple had been glazed, and trees that were smaller even than bonzai were dotted all over the otherwise grassy and mossy gardens.  They were beautiful, elaborate constructions, almost certain a work of art, and yet here was this man trying too hard to be the salt of the earth, claiming that he'd just found them when digging things up and that they might actually be genuine.
"The houses are beautiful," said Dr. Malmstein thoughtfully.  "The artist should probably exhibit them somewhere where they'd get more attention."
"There's no artist," said the man with the cap, looking scandalised.  "There's just me.  I dug them up, and I'd like some reassurance from you clever types that my skull's not going to be next!"
"There would surely be some small difficulty in extracting it," murmured Dr. Malmstein, but quietly enough that only Bob heard him.  "Well, Mr. Phelps, I'll have my assistant query the quipping machine about it, and we'll see if that can offer better advice.  It's a true wonder of modern technology, you know."
Bob flinched.  He'd been avoiding MSPARKER, the university's quipping machine ever since she'd sent him a list of doomsday scenarios.
"I'm not sure that's a good use of university fun–" he managed before Dr. Malmstein caught his gaze and silenced him.
"It is," he said firmly.  "Ask MSPARKER what the point of the skulls might be."
"And what the houses are for," said the man quickly.  He looked slightly more shifty when he smiled.
"Oh fine," said Bob, his voice betraying his irritation.  "Give me twenty minutes to check she's awake."