Harry Connick Jr. is a genius. This is a famous clip for a reason. He is performing for a live studio audience in France. The crowd is really enjoying it and clapping along.
The problem is they are enthusiastically clapping on 1 and 3 with no end in sight.
But Harry has a plan. He slips a 5/4 bar in at the 0:39 mark so smoothly that no one even notices.