School counselor Mr. Mackey calls Liane Cartman into his office because Eric Cartman handcuffed Billy Turner's ankle to the school flagpole, then gave him a hacksaw to free himself. While discussing her sons worsening violent behavior, she begins to cry. Cartman tries to lighten the mood by singing this song.
Cartman: You're a great mom.
Who's got the greatest mom in the world?
My mom is number one in my heart.
Mrs. Cartman and Cartman: My mom's the best mom, better than your mom.
It's singing together in harmony.