Some of the nearly 400 proposition bets for Super Bowl 50 between the Carolina Panthers and the Denver Broncos are displayed at the Race & Sports SuperBook at the Westgate Las Vegas Resort & Casino. (Ethan Miller/Getty Images)

The fat man plowed over the goal line, and across Las Vegas phones started ringing in the back offices of sports books. One of them rang at the old MGM, where Jimmy Vaccaro picked up the phone. The panicked voice on the other end asked what bookmakers all over town wanted to know: “What the [heck] just happened?”

What had started as a lark, a goofy way to drum up business, had led to widespread commiseration. The books had offered bettors a chance to bet on William “Refrigerator” Perry scoring a touchdown in the 1986 Super Bowl, the most exotic version of a proposition bet — a “prop” — offered to that point on the biggest sporting event in the country. When Perry plunged into the end zone during the Chicago Bears’ blowout over the New England Patriots, it stunned the oddsmakers and cost Vegas casinos vast sums.

What the [heck] really happened was this: Perry’s unlikely touchdown gave rise to a phenomenon that changed the way millions of Americans watch the Super Bowl. Americans will wager $4.2 billion on Super Bowl 50, according to the American Gaming Association’s projection, and it would be a conservative estimate that $1 billion will be risked on props — bets pertaining to specific outcomes within and surrounding the game other than the actual score or total number of points.

Do you think the Denver Broncos will score exactly four points? You can bet $100 on it at the Westgate Las Vegas SuperBook and win $999,900. You can predict which player scores the first touchdown, or whether Neymar will score more goals Sunday than Cam Newton scores touchdowns, or how many receptions Carolina Panthers wide receiver Jerricho Cotchery will make. You can bet, at worse than 50-50 odds, on the coin toss.

William "The Refrigerator" Perry spikes the ball after scoring a touchdown that cost Vegas book makers dearly. (Amy Sancetta/Associated Press)

At the Westgate, for one, bettors can choose from more than 400 props, including — this is real — whether the total points and rebounds on Sunday by Sacramento Kings center DeMarcus Cousins, subtracted by 6 1/2 , will be less or more than Broncos tight end Owen Daniels’s receiving yards. Offshore and online sports books, not held to the same regulation standards as the Vegas casinos, offer odds on how long the national anthem will last, what color the Gatorade dumped over the winning coach will be and which song Coldplay will play first at halftime.

“Now,” Wynn sports book director Johnny Avello said, “it’s just grown into a monster.”

‘I was sweating bullets’

This year’s Super Bowl will mark the 30-year anniversary of when the madness began to escalate. Entering Super Bowl XX, “proposition wagers were really an unknown commodity,” said Station Casinos Vice President Art Manteris, who ran the Caesars sports book in the mid-1980s. Sports books offered a handful for big games, simple stuff such as the result at the end of each quarter.

Manteris wanted a way to attract more casual fans to his sports book. The Bears were fashionable, a team that went 15-1 during the regular season with players who taunted the commissioner and danced the Super Bowl Shuffle. No player was more lovably popular than Perry, a mammoth, rookie defensive tackle whose gap-toothed smile had appeared in commercials and on David Letterman. Perry had scored twice in the season as a goal-line fullback, which only added to his aura.

Manteris believed a bet involving Perry would appeal to average fans. His assistant and close friend Chuck Esposito assured him Bears Coach Mike Ditka would never risk a defensive lineman fumbling in the Super Bowl, and anyway Perry hadn’t rushed the ball in nearly two months. Manteris set the line at 20-1: for every dollar someone bet, they’d win $20 if Perry scored a touchdown. (Vaccaro, now the director at South Point Casino, put up the same line an hour later at MGM. “Me and Manteris, we still wrestle over that,” said Vaccaro, who defers to Manteris as the progenitor “even though I’m older.”)

The ploy worked. Bettors poured into the sports book to bet on The Fridge scoring a touchdown. Other sports books copied the prop. The Associated Press picked up the story, and newspaper reporters from Chicago started calling Vegas. As bets come in, bookmakers adjust the odds to mitigate their risk. So many people flocked to Manteris’s prop that by kickoff, the odds had fallen to 2-1.

“The Refrigerator prop got so much attention,” Manteris said. “The PR department had so much fun with it.”

A betting sheet for Super Bowl 50 between the Carolina Panthers and the Denver Broncos is displayed at the Race & Sports SuperBook at the Westgate Las Vegas Resort & Casino. (Ethan Miller/Getty Images)

For Manteris and his cohorts, the fun stopped late in the third quarter. With the Bears leading 37-3 and at the 1-yard line, Ditka sent Perry into the backfield. The sports book erupted when Perry rumbled into the end zone, everyone elated except the bookmakers in the back offices.

“I remember it like it was yesterday,” Manteris said. “I was sitting in the office with Chucky Esposito. I wasn’t real happy. He had assured me a million times, ‘He’ll never carry the ball.’ ”

Vaccaro said his sports book lost $48,000 on the touchdown, but “Art won the prize that day.” Manteris would not reveal the precise figure, but said he lost well into six figures. The next day, Manteris received a call from the chairman of the casino.

“I was sweating bullets,” Manteris said. “I thought he was calling to ask how we could lose so much money on a stupid prop.”

Instead, the chairman congratulated Manteris on the attention the wager had brought the casino. The Fridge Prop had paid for itself in publicity.

“It was the best money ever spent by the sports books in Las Vegas,” Vaccaro said.

‘We knew we had something’

The popularity of the Perry prop made bookmakers realize what a huge draw they could be. In 1989, a young bookmaker named Jay Kornegay opened the sports book at the Imperial Palace and pushed them further. By then, most sports books offered around 25 props. For the 1990 Super Bowl, Kornegay, who now runs the Westgate book, proved he could branch outside football to create a Super Bowl prop bet: Who would score more, the San Francisco 49ers or Michael Jordan? (Joe Montana’s 49ers cashed, 55-39.)

A string of Super Bowl blowouts in the early ’90s lessened betting interest on the game, so Kornegay offered more props. In 1995, when the 49ers were a 19 1/2 -point favorite over the San Diego Chargers, Kornegay tripled his book’s menu to roughly 150 props, with a focus on results that wouldn’t be decided until late in the game.

“From that point on, we knew we had something,” Kornegay said. “Everybody warmed up to it.”

Props have only grown in diversity and popularity. Manteris believes the rise of fantasy sports, which conditioned fans to calibrate individual stats, pushed more casual bettors toward props. The prevalence of online sports books pushed the Vegas casinos to expand their prop menus, but only to a point. State regulations prohibit casinos from taking bets on action that can be known ahead of time or is voted upon, although the gaming commission is starting to relax its standards. For this time this year, Vegas casinos can take bets on who will win the MVP. Cam Newton is the favorite at 5-7 odds.

As those props piled up, so, too, did the war stories. In 2007, a frequent high-stakes gambler at Manteris’s casino wanted to bet above the typical limit that Chicago’s Devin Hester would score the game’s first touchdown against the Indianapolis Colts. Manteris assented.

“The opening kickoff of the game goes to Hester, he takes it back [92] yards and scores the first touchdown,” Manteris said. “I look at some of my guys and go, ‘Holy [smokes], we’re nine seconds into the game, and we’re stuck $100,000.’ ”

If you like the look of ashen faces, mention Super Bowl safeties to a Vegas bookmaker. In 2012, the New England Patriots took possession on their own 6 in a scoreless contest. Tom Brady backed into his own end zone, rifled a pass out of bounds and got called for intentional grounding, an automatic safety. Not only did those holding a ticket betting “yes” on the question of “will there be a safety?” cash in, but so did those who wagered on the first score being a safety – at 100-1 odds.

The books got clobbered, and the result encouraged bettors to bet on the safety next year. As the Baltimore Ravens protected a five-point lead in the shadow of their end zone, they took an intentional safety, which meant more winning tickets for those who bet on any safety or a safety on the final score. Lightning struck again in 2014, when the first snap of the game flew over Peyton Manning’s head and rolled into the end zone. Another first-score safety, and another beating for the books.

“Safeties, they can eliminate that as far as I’m concerned for the Super Bowl,” Avello said. “When a guy gets sacked in the end zone, just make it worth six points.”

‘There’s no algorithms’

Some lines are easy to determine. At South Point, Vaccaro has taken $30,000 in bets on three props he posted the day after last year’s Super Bowl: whether there will be a two-point conversion, whether there will be overtime and the coin toss. The bets came in small amounts, none larger than $50, from tourists who wanted to know they’d have a little action on the big game.

Others take more time. At the Wynn, Avello orders an Italian feast for his team of six at 5 p.m. on the Thursday after the conference title games, and they stay up all night until they’re finished. They scour statistics from the year, study how the teams fared against common or similar opponents and try to gauge public perception. “There’s no algorithms that need to be done,” Avello said. Avello checks and double-checks the language. By Saturday afternoon, the full menu is ready for the public.

“It wears me out,” Avello said Wednesday afternoon. “I’m just starting to come around. It’s almost like I had a head cold for four days.”

Thirty years after Perry’s touchdown captured the public’s eye, props are more popular than ever. Kornegay expects 60 percent of the Westgate’s Super Bowl “handle” — the amount of money bet — to be on props. Bookmakers are still seeking creative means to let customers bet on the game’s biggest stars. Vaccaro created a prop asking whether Manning will finish the game. The line for “yes” is -400, and “no” opened at +300. It’s perfect, really: the game’s biggest story line and a bet that could come down to the final whistle, no matter the result of, you know, the game.

“Every year,” Vaccaro said, “someone somewhere comes up with something neat.”