Who will succeed the media mogul Logan Roy at Waystar Royco, the global entertainment juggernaut at the center of HBO’s “Succession”?

It is the perennial question that the show has tried to answer since it premiered in 2018, and amid its fourth and final season, it’s one that Sophia Meng is betting on with a group of five friends, who are each wagering at least $200.

“I’m betting on Kendall, but with devastating effects on his personal life,” said Ms. Meng, 24, an illustrator in Brooklyn, referring to the actor Jeremy Strong’s character. “A hero’s journey, ending back home, but the home is different. Like, you got everything you wanted, but you’re still nothing.”

Ms. Meng is one of several “Succession” viewers hoping to find out, and cash in on, who will be the next heir of the show’s media empire, with rewards reaching as much as $1,000. No longer limited to sports, betting has become a part of the viewing experience for both popular television shows like “The Bachelor” and fictional dramas. (While wagering on television shows on some websites can run afoul of gambling laws, “casual social betting among friends” is legal in most states, said I. Nelson Rose, a gambling lawyer and expert.)

“Succession” has earned acclaim for its depiction of the fictional lives of the mega-rich, power-hungry and venal Roy siblings (Connor, Kendall, Shiv and Roman) as they vie for control of Waystar Royco. Almost every component of the TV series has found a second life elsewhere in culture, inspiring a Twitter account with more than 255,000 followers that posts out-of-context scenes from the show, weekly commentary about the cast members’ fashion and even a remix by the rapper Pusha T of the series’ catchy theme song.

It is this kind of fandom that has culminated in a “mini-version of a Super Bowl” for the show’s finale, said Ms. Meng, who is in the running for a $1,000 jackpot. “I might spend it on a trip to Tuscany.” (The location of the drama-filled Season 3 wedding of Caroline Collingwood, Shiv, Kendall and Roman’s mother, on the show.)

Jayson Buford, who placed a $20 bet with nine of his friends at his “Succession” watch parties, said betting was “a fun activity to do to supplement the idea of the show, which is very communal. It’s a show about a family, people have watch parties, people gather, and it plays within that.” Mr. Buford believes that Waystar Royco is going to dissolve and that nobody will take over the company. Logan “thinks Kendall is an addict, and he doesn’t think Shiv is smart,” he said.

Some “Succession” viewers are placing noncash bets to bond with their co-workers. “It’s a team-building exercise,” said Colm Phelan, 30, a digital public relations manager in Dublin. “Everybody was watching ‘Succession,’ and we thought it’d be fun to start an in-house gambling game for the team.”

About 25 participants place pretend $10 bets every Monday, Mr. Phelan said. Contestants can change their guesses based on the outcome of the latest episode each week, but by the end of the series, only the person who correctly chooses the successor the most number of times will be named the winner. The prize? “T.B.D.,” he said. “It wouldn’t be a cash prize; it would be a gift voucher.”

Shruti Marathe, who started wagering money on television shows with her group of seven friends from college when “Game of Thrones” aired its sixth season in 2016, has expanded her casual betting game to a somewhat time-consuming hobby that now includes more than 60 participants across five different social circles, three rounds of predictions and an elaborate survey that goes beyond the question of who will come out on top. (Cash is no longer involved.)

The groups include Ms. Marathe’s work friends, her college friends, her non-college friends and her family and their friends. There’s also one she calls “The Waystar Royco Executive Training Program.” Who’s in this latter group? “Friends of friends,” said Ms. Marathe, 25, a development manager in Los Angeles. “For example, people who were sitting at my table at my friend’s wedding.”

The 15-question “Succession” form requires players to forecast several potential plot points: whether Logan or Kendall will die before the series finale; if Gerri Kellman, Logan’s long-suffering counsel, will “proactively initiate a romantic or sexual” relationship with Roman; when Shiv will confront her husband, Tom, about his betrayal in the finale of Season 3; and whether Connor will drop out of the presidential race.

Because of the survey’s detailed responses and number of participants, Ms. Marathe said, she chose not to collect money from players, so there will be no official cash prize. But winners will receive something priceless: “You get bragging rights,” she said.