This week’s installment of The Rehearsal boldly answers the question “What if the movie Sully starred Nathan Fielder instead of Tom Hanks and took place inside a 19th century carnival performer’s feverish nightmare?”

The episode opens with a stunt involving Fielder’s attempt to revive the personality of a dead dog via its clone. Then, in a left turn so wide that it mounted the curb and hit several pedestrians, Fielder endeavors to try out this “personality transfer” approach on himself. And because this season is all about aviation safety, the personality he tries to hack into is that of Captain Sully Sullenberger.

Using Sully’s 2009 memoir Highest Duty as his road map, Fielder restages key moments in the pilot’s life, experiencing them firsthand. It all begins in infancy, a feat that’s accomplished with gigantic sets and towering puppets. Of course, Baby Nathan doesn’t actually...