On April 28th, 1967, Muhammad Ali stood in a line of 46 men on the third floor of a Houston induction center while Lieutenant Steven Dunkley read the rule: take one step forward when your name is called, and the step itself puts you in the Army. The heavyweight champion of the world had spent the morning taking the physical and turning down a ham sandwich. Officers called his name 3 times, warned him that refusing meant a felony, 5 years, and $10,000, and got a written statement instead.

The step would have cost him almost nothing. The government had offered his lawyers "all kinds of deals," no combat and no rifle, just boxing exhibitions for the troops, the same arrangement Joe Louis had in World War II. Sugar Ray Robinson begged him to take it. Elijah Muhammad forbade it, and the last man who defied the Nation of Islam was Malcolm X. Ali's feet never moved.

What if they had?

This week we hit CTRL+Z on the step he refused, and follow the ripple to today: a quiet Sunday in Cleveland, a nickname that stays on a Harlem playground, a swimmer lighting the cauldron in Atlanta, and a roll call at the 2016 ESPYs that runs 1 name short. Nobody ever marches behind Muhammad Ali, because on the one afternoon it counted, Cassius Clay stepped forward.

SPOILER ALERT: This episode discusses the endings of The Sopranos, Breaking Bad, Lost, Parks and Recreation, Mad Men, The Leftovers, and Ozark.

On June 10th, 2007, David Chase ended The Sopranos with a family eating onion rings in a New Jersey ice cream parlor, a bell over the door, and 10 seconds of black. Viewers across the country hit their cable boxes. The Boston Globe's television critic sat through those seconds certain his set had died and taken the review with it.

Chase had spent years planning something else. Tony Soprano drives out of the Lincoln Tunnel at the top of all 86 hours of the show, and the last scene sent him back the other way, into Manhattan at night, to a meeting he wasn't walking out of. Then, driving down Ocean Park Boulevard in Los Angeles in 2005, Chase passed a little breakfast place, and a thought arrived: Tony should get it somewhere like that. The breakfast place won.

What if it hadn't?

This week we hit CTRL+Z on the last pages of the final script, and follow the ripple to today: a song that stays where it was in 1981, a corner booth in Bloomfield that stays furniture, a documentary that ends on an answer, and a decade of showrunners deciding what they owe an audience when the credits come. Nobody ever asks David Chase what happened to Tony Soprano, because 12 million people watched it happen.

On May 9th, 1933, guards climbed a scaffold in the lobby of the RCA Building and brought Diego Rivera down mid-brushstroke. His fresco for Rockefeller Center held a portrait of Lenin, and Rivera had refused Nelson Rockefeller's written request to paint it out. The wall got a canvas drape, and 9 months later, workmen chiseled 63 feet of plaster into powder near midnight.

Buried in Rivera's refusal letter sat a counteroffer almost nobody remembers. He would trade the mural's nightclub scene for Abraham Lincoln, standing with John Brown, Nat Turner, and Harriet Beecher Stowe. Lenin on one side, Lincoln on the other. Nelson, 24 years old, said no.

What if he'd said yes?

This week we hit CTRL+Z on May 8th, 1933, and follow the ripple to today: a finished fresco drawing Depression crowds past a communist in a capitalist lobby, a congressman waving photographs of the wall on the House floor, a velvet curtain going up in the McCarthy years and coming down for a funeral, and delegates at the 1964 Republican convention booing the man who kept it. Rockefeller Center destroyed the painting, hired another artist, and put Lincoln on that wall anyway. The mural Rivera lost became the most famous artwork America ever destroyed, and the version that survives hangs in an office lobby where tourists walk past it on the way to the elevator.