The Cheese Man was an enigmatic figure manifesting in the dreams of Buffy, Giles, Xander and Willow following their performance of the Enjoining spell and the death of Adam. He was always seen with cheese slices and making comments about them, hence his alias.
Behind the Scenes
He was portrayed by David Wells.
He was allegedly intended to be the only truly random, chaotic thing in the dreams that otherwise explored the gang's personal fears and failures.