"I Saw a Big Parade" is a song from "The Egg." It is sung by Gumball and Darwin, who make up the lyrics as they sing.
Gumball: I was walking down the road one day
And I saw a big parade
It was green and had things in it
Darwin: And more balloons
Both: Fourteen hours later...
We were having the best day with our friends...
Gumball: And happiness together
That's why we
Darwin: Why we smile