How about some ghostly chit chat?

In the midst of the Great Hall, a transparent grey figure flew past the banners of the four houses. It seemed like the ghost had a specific destination, as it seated himself or levitated himself on the chair to the empty table.

Now that was a first, usually all the tables were full at this time of the morning, but the ghost seemed determined. When the face of the ghost came into clear view, it was the handsome face of Sir Nicholas de Mimsy Porpington.

Sir Nicholas leaned forward to the food that lay before him, and wasn't surprised to see that it went right through. Now where were his fellow ghost mates?

Fat Friar flew into the Great Hall quite early in the morning-well, it wasn't actually that early but to him it was. He was used to sleep in and appear late in the morning, but today his intentions were ruined by an annoying owl screeching next to him. No, he did not receive a letter, the owl was for someone else in the Hufflepuff tower and apparently, it was hungry. So hungry it had to wake up a ghost. But Friar was only annoyed for a minute, then he thought of food and immediately floated down to the Great Hall.
He saw the Gryffindor ghost, Sir Nicholas sitting by a table, smelling food or whatever it was he was doing. Friar flew up to him, smelling the delicious food all around him. Shame he wasn't able to eat anymore. Such a shame...

"Good morning, Sir Nicholas! Dwelling on the thought how it was to eat, are you?" he said, floating through some of the hot chocolate croissants.

When the Fat Friar appeared, Sir Nicholas jumped a little, not expecting someone else to have seen him do that. The Gryffindor ghost nodded sadly, "Indeed I was sir, it is one of the things I miss most about the human life".

"And what brings you here so early in the morn?"