The portly ghost was almost eating at Sir Nicholas de Mimsy-Porpington’s 500th Deathday party on Oct. 31, 1992. Nick provided a long table of food for his guests with rotten fish, burnt cakes, maggoty haggis, mouldy cheese and a cake in the shape of a tombstone. Harry watches as the portly ghost walks through the table and puts his mouth through the stinking salmon.
Other canon notes and references
He is a wizard (OP38).