Cocktail ice should be formed like a duck, swimming on the beverage.
He created a very spherical sphere. I twizzled it round and round but could not detect any eccentricity. Clearance in the tumbler was even at all orientations.
A carved duck might be more immediately impressive, but the sphere did blow my mind.
It was a very good old-fashioned. I nursed it for 20 minutes - it didn't get watery, as they usually do.
Edit: though I would bet that’s less of a factor than the initial temperature of the ice and the liquor.
Look at the huge jump at 0 deg C in this diagram: https://upload.wikimedia.org/wikipedia/commons/9/9d/Heat_cap...
It takes less heat to warm ice from -100 C to 0 than it does to melt ice at 0 C to water at 0 C.