 In one scene of the episode , Homer sprays two bottles of lighter fluid onto his grill , causing viewers to anticipate an explosion when Homer throws a match on it . When he does release the match , however , the grill barely ignites . A similar scene appears in an older episode of The Simpsons , " Treehouse of Horror " , although in that episode , Homer uses a single bottle of lighter fluid and causes an explosion . Mirkin enjoyed the joke enough to reuse parts of it in " Lisa the Vegetarian " , adding new twists to further enhance the comedic effect . The old sketches from the " Treehouse of Horror " episode were used to help the animators animate the scene . 
