The thing that couldn't be done

Somebody scoffed: Oh, you'll never do that;
At least no one ever has done it
But he took off his coat and he took off his hat,
And the first thing we knew he'd begun it.

With a lift of his chin and a bit of a grin,
Without any doubting or quitting,
He started to sing as he tackled the thing
That couldn't be done, and he did it.