This story was based on a writing prompt image of a large statue of a horse head, somewhere in the UK.
Doug spent most of his time with a rubber horse mask trying to scare me.
He turned his considerable intellect to find the most disturbing ways for me to encounter the mask. He actually hired a dog – apparently you can rent dogs now – and attached the mask to the poor animal’s head so that it charged around, flopping grotesquely and smashing into all the delicate electronics that was my contribution to our project. He bought a store dummy that he could position with the mask in unexpected locations. And of course the inevitable time he broke silently into my house and put it on my pillow while I slept, Godfather style. Each time I wanted to quit, find another sub-quantum physicist with a better sense of humour, and each time he’d finish laughing, wander to the blackboard and create the most beautiful mathematics I’ve ever seen.
The final prank he pulled was the simplest of them all. He just put the damn thing on and stood directly behind me, very quietly, until I turned around.
I don’t know how long he stood there for. I do know that it took me completely by surprise. I pushed him, hard, right into my fragile device, where his body connected two electrodes that were not meant to circuit. Even as electricity burned across him he crushed through the device and vanished, while I looked stupidly at the wreckage of our time machine.
I was still staring stupidly when he returned, seconds later. He was scarred, carrying a version of our machine made from copper and diamonds. Still wearing the horse head mask.
Doug waved my apologies away and sat, looking smug. He refused to talk about what had happened.
As I left I saw that damned thousand year old horse statue.