Mary Lou Helperman

Mary L​ou Helperman (voiced by Debra Jo Rupp) Leonard's mother, and the teacher of his fourth grade class. She is a beautiful, nice, lovable person who likes to inject humor into the fourth grade class. Leonard is somewhat embarrassed about his mom being the teacher and Mrs. Helperman loves to embarrass him.

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Mary becomes Leonard's new teacher after earning a teaching degree. She buys him a purple bunny backpack but Leonard angrily turns it down.

At school, she meets Scott Leadready 2 unaware that he's really her dog. And Scott instantly becomes the most popular and Leonard becomes envious. When Leonard finds out, he, Scott, and Ian decides to run for president. And Ian wins by 1 vote.

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At the end of the year, she gets nominated for a teachers award and the principal lends her his RV only no pets are allowed so, they leave Spot, Pretty Boy, and Jolly at home.

At a gas station, she meets Scott and he convinces her to take him along (along with his "family").

When they arrive, she leaves the boys at the beach. Who later go to Dr. Ivan Krank to make Spot's dream come true.

Back at the RV, Scott (who's now a grown man) and Leonard forget how Scott is a man. She invites human Spot for dinner and falls in love with him. After a long fight with Leonard, Spot leaves the Helpermans forever.

The next day, Mary goes to the awards ceremony while Leonard is in bed crying.

After Spot is turned back to a dog, Leonard is at the awards ceremony and she has won. Spot, Pretty Boy, and Jolly are outside cheering for her.

That night, Spot is dressed up as Scott and convinces Mary to take him home with them and Jolly and Pretty Boy are hiding under the RV's bed as part of Scott's plan.