Mac: (Playing with toy cars with another kid outside on the sidewalk) Vrooom! Vrooom! Ert. Ert.
Kid: No, no.. It would sound more like this - (Opening mouth wide as a car screeching is heard)
When the other kid corrects Mac it appears at first that a real car sound is coming from his mouth, but we soon discover it is actually Bloo driving the Foster's bus right at them and screeching the tires. This parodies Gerald McBoing Boing, a series geared towards younger children about a boy who can only communicate by producing sounds with his mouth.