Because it sounds better than him singing.
Good stuff! The winner is…
Thanks, Professor! Continuing the misplaced-animals theme, I guess:
Joe Penner has a man bun?
I’m a little white duck riding on a backpack
A little white duck, gonna ride on Amtrak 
Have duck, will travel.
“Hello Cecil? I’m using an echo chamber but I can’t get the duck to quack.”
It’s 12:35 AM; of course he’s on his way to Walmart.
I liked all the answers but this one tickled my risibilities the most:
So, Winston, take it away!
Thank you. Let’s keep it on a theme (kinda)
Run! Giant Ernie won’t be far behind!
An ominous entry to Echo Plaza.
“Why a duck?”
“Why a no chicken?”
“I catch ona why a horse”
The only 1950s “atomic testing gone bad” movie ever shot in color and it had to be about THIS!
EGON: Ray… what did you do?
RAY: I couldn’t help it. It just popped into my head. I thought of the most innocent thing from my childhood: Ernie’s rubber ducky.
That’s nothin’. You should see the lamb.
So which do you mean for me to do – “run for cover” or “duck?” Oh, I see now.
We’ve got a winner! Elmer, you’re up!
Well, what the duck…
What happened to the rest of the Usual Suspects?