Finding a better word for jacket proved more difficult. He tried “whole-upper-body clothing,” then “man’s upper half,” until settling on “man torso” or “torso.” “I like ‘torso’ because it’s common and uncommon,” Mr. Kaplan said. “People know what it means but don’t use it often.”

The first week is arguably the most creative in the life of a joke. For Mr. Kaplan it’s all about generating ideas. What could explain this jacket convention? Maybe, he speculated, jackets were once very cheap and, as he would later say onstage, “men wore seven coats out, hoping it wasn’t an eight-puddle day.” He also decided that the modern equivalent was leaving the toilet seat down.

All these ideas were transformed into jokes as the bit expanded. Setups shrank. Punch lines multiplied. The jacket over the puddle soon became one of several examples of chivalry that began with his pantomiming opening a door after asking the audience: “Does it detract from chivalry if, when opening a car door for a lady, I say, ‘Chivaaalry!’ ” He dragged out the last word in the self-satisfied voice of a magician introducing his assistant. A coarse joke about chivalry during sex replaced the homeless-man line. “It had a more powerful impact,” Mr. Kaplan said.

By early January Mr. Kaplan’s rhythm became more assured and moseying, lingering on pauses, finding extra laughs between punch lines. His typical stage pose — leaning back, his free hand placed gently on his stomach as if he were pregnant — became looser, adding touches of showmanship.

It didn’t matter where he performed (clubs, restaurants, even a hostel), chivalry always worked. The focus now was on getting the right laughs. It was important, he thought, to get a big one right at the start with his car-door opening, and in paring it down, he turned a question (“Does it detract from chivalry ....”) into a statement. Later, he brought back the question. Laughter marginally improved.