▁M irk in ▁enjoyed ▁the ▁jo ke ▁enough ▁to ▁reuse ▁parts ▁of ▁it ▁in ▁" L isa ▁the ▁Veg et arian ", ▁adding ▁new ▁tw ists ▁to ▁further ▁enh ance ▁the ▁com edic ▁effect . ▁The ▁old ▁sketch es ▁from ▁" Tree house ▁of ▁Hor ror " ▁were ▁used ▁to ▁help ▁the ▁anim ators ▁animate ▁the ▁scene . ▁ ▁Cultural ▁references ▁The ▁episode ▁features ▁several ▁references ▁to ▁The ▁Beat les ▁and ▁McC art ney ' s ▁solo ▁career . ▁For ▁instance , ▁McC art ney ▁tells ▁Lisa ▁that ▁playing ▁his ▁ 1 9 7 0 ▁song ▁" Maybe ▁I ' m ▁Ama zed " ▁backwards ▁will ▁reve al ▁" a ▁reci pe ▁for ▁a ▁really ▁r ipp in ' ▁l ent il ▁soup ". ▁A ▁modified ▁version ▁of ▁the ▁song ▁plays ▁in ▁the ▁final ▁scene , ▁then ▁over ▁the ▁closing ▁cred its ▁of ▁the ▁episode ; ▁when ▁played ▁backwards , ▁McC art ney ▁can ▁be ▁heard ▁rec iting ▁the ▁reci pe ▁in ▁the ▁song . ▁M irk in ▁had ▁McC art ney ▁record ▁the ▁reci pe , ▁which ▁was ▁later ▁added ▁in ▁reverse ▁over ▁the ▁original ▁song . ▁McC art ney ▁thought ▁it ▁was ▁" very ▁fun ny " ▁that ▁the ▁staff ▁wanted ▁to ▁" send ▁up ▁the ▁whole ▁cult ▁thing " ▁of ▁back mask ing ▁on ▁the ▁Beat les ' ▁songs . ▁" A ▁secret ▁l ent il ▁soup ▁reci pe ▁seemed ▁a ▁nice ▁par ody ▁of ▁that ", ▁he ▁said . ▁One ▁of ▁the ▁backwards ▁sni ppets ▁says , ▁" Oh