"A New Start" is a song from The Amazing World of Gumball. It is sung by Gumball and Darwin in the episode "The Kids" while their voices are broken and deep, just before the two main characters get their new voices.
Gumball: Maybe it's for the better.
No-one wants to stay a child forever.
Darwin: Remember the wonderful times we've had.
Those happy thoughts now make me sad.
Both: They say it's not bad.
It's just a new start.
So why do I have this pain in my heart?
Our childhood memories are getting hazy.
But soon we can drive, go to college, and we both go crazy!