Lou is first seen sitting while the other Bar-ba-loots climb on his back to reach a bar-ba-loot fruit. He is later seen dancing with the other forest creatures while the Once-ler sings but then prepares to attack the Once-ler until he (and the other animals) began to eat his marshmallows. Afterwards, he and the other forest creaturs watch the Once-ler chop down the first Truffula tree and then when the Lorax comes he tearfully mourns the tree with him and the other creatures.
He later tries to help save the Once-ler and Pipsqueak from going over the waterfall. The next day he is in the Once-ler's house (eating the butter in his fridge). When the Once-Ler's relatives convince him to chop down the trees for their Thneed businesses, Lou and all the other forest creatures suffer from the deforestation. After the very last Truffula Tree is chopped down, the Lorax sends Lou off to find a better place along with all the other animals.