wondering whether Godzilla was a biological creature at all as opposed to, for instance, a giant robot left behind by an advanced and forgotten civilization

That's one of my main take-aways from PT:TLOS so far. (This post has reminded me of one of the exercises in the book.) The idea in Chap. 5 that given extremely unlikely priors for a hypothesis, strong evidence appearing to favor that hypothesis will not so much confirm it as call for the the resurrection of another, highly unlikely, but still more plausible than the original.

"You are being deceived" is advanced as a useful hypothesis to consider resurrecting in general. Perhaps conspiracy theorists are not as stupid as they sometimes appear; if you think the straightforward hypothesis unlikely enough, mass deception can be a more appealing hypothesis, with readily available mechanisms of explanation. (For instance a movie like The Truman Show couldn't work if we didn't assign a small degree of plausibility even to mass deception, given sufficient financial incentive.)