Which one? There's two. One of them is Baffler Meal, the one that got shelved but eventually spun off into Aqua Teen Hunger Force. And that episode replays in my brain at least once a week.
"Go on Ghost...tell him what you fight."
"I...I fight hunger, Willie."
"Louder. Be proud of what we make you do."
Willie probably got along great with the Space Ghost/Williams Street crew because they were reportedly stoned all the time.