... this is the hapless two story average American home mentioned here. It is a series of motion picture frames from "Operation: Upshot Knothole" that we have seen over and over. Only recently have I spotted what appears to be an American Standard toilet being ejected out the back of the dwelling (?)
In the second frame and the enlargement it certainly seems shaped like a toilet.(enlarge each image by: right click/open in new tab) The test house had furniture, mannequins a kitchen. I suppose it would make sense to have a bathroom. Or at least a basic W/C so the doomed store-dummy family would have a place to re-leave themselves as the seconds ticked down to zero.
The initial position and trajectory seem a bit high, unless it was in the attic. However the house is simultaneously collapsing, being pushed backwards and the roof is peeling back. If the toilet was connected to a sturdy waste stack then it is possible that it is simply 'holding it's own' while the house is being blown apart around it.
Given the mystery of "the stray shoe" (see link above) it is also possible that the Corporal in charge of installing the toilet simply stashed it in the attic: not knowing that 61 years later his slovenly actions would be discovered!