Once-ler lived with his mother, brothers Bret and Chet, uncle Ubb, and aunt Grizelda. They all thought he would "do nothing", so when the Once-Ler left to sell his invention, Thneed, they were happy to laugh at his optimism. Despite this, the Once-ler continued on his journey to find the perfect material for his Thneed. While he was playing songs with his guitar, after being pulled by his mule in his full car for a while, he came across "the most beautiful place he had ever seen". The valley was filled with trees, Bar-ba-Loots, Swommee Swans, and Wuthering Fish, who had nothing against him.

As he cuts down his first tree, the Lorax is summoned from the thunder in the sky and takes shape in the tree stump. The Lorax warns him, but the Once-ler does not find him threatening.

The night he arrives, while he is sleeping peacefully, Lorax retrieves his bed and pushes him into the river with the help of Bar-ba-Loots, Swommee Swans and Humming-Fish. Unfortunately, their plan is ruined because one of the youngest Bar-ba-Loots also finds herself in bed but can't swim.

Lorax rescues Bar-ba-Loot, Pipsqueak and Once-Ler and they strike a deal. Once-ler promises not to cut down any more trees, but in return, Lorax says he will help him. As time passes, the Once-ler's Thneed is discovered and highly valued. To fulfill this request, the Once-ler summons his family to the valley to help him make the Thneeds. His mother wants him to start cutting trees to speed up production, and he does so under pressure.