Butt-Scratchers are what Peter sold to help pay for Chris's education in "No Chris Left Behind". He would sell them at a baseball game in an vendor-like fashion yelling, "butt-scratchers!'.
In "Baby, You Knock Me Out", a barker can be heard yelling "Buttscratcher!" in the audience at the Deirdre Jackson/Lois Griffin fight.
In "Peter's Sister", a Butt-Scratchers vendor can be heard at the New Haven Coliseum during Peter's wrestling match with his sister, Karen Griffin.
In "Peter's Def Jam", Peter shouting "Buttscratcher!" is part of his DJ music.