The latest issue of Fortean Times (FT403 March 2021) has a small article about unusual ghosts - unusual as in non-humanoid. As well as a haunted lamppost, and a giant luminous crab, there is a tale as recounted by Third Doctor Jon Pertwee, of a ghostly encounter he had as a small boy.
He was the guest of a school friend at an Elizabethan house in Sussex. There were many other guests, and the friend he was staying with seemed uncertain about the room that Pertwee was to sleep in. The boy's mother assured him it would be okay as children tend to be deep sleepers.
On the first night, Pertwee woke up feeling nauseous, and threw up over the bedclothes. He had no explanation for this illness, which soon passed.
The next night however, he woke up to smell a terrible stench in the room, as of rotten meat. He then witnessed a glowing green object, similar to a tree stump, at the foot of the bed, which moved slowly across the room. He was so frightened that he wet himself and ran out of the room to where others were sleeping.
The family were obviously aware of this apparition but thought that, as a child, he would sleep through any manifestation.
Now Pertwee was a great story-teller, especially if it involved himself, and he would often elaborate and expand on his own role in the narrative. What makes this story sound plausible is the strangeness of the thing he saw (and smelled). Most kids making up ghost stories would have gone for the headless Tudor, or the hooded monk, or the spectral lady in white - something traditional being more likely to be believed. The sheer bizarreness of Jon's experience suggests that it might possibly have been true. Who knows...?