Meenan is surprised that other teams in the MLB lack similar groups but has stopped giving out pointers to other fan bases about how The 7 Line built its success. Several groups have blatantly attempted to rip off its business model, but none have had any long-term success, he said.
The 7 Line's thundering support has been noticed by a very important group — the Mets team itself.
"In Baltimore, [outfielder Curtis] Granderson gave us a shout-out: 'The 7 Line Army is here!' And [pitcher Jacob] deGrom in the post-game interview said it felt like a home game. During that game, I had to look around and realize that we weren't at Citi Field," Meenan said.
The Mets trip to the 2015 World Series has given this long-suffering group of fans a lot to cheer about (even though, per Elias Sports Bureau, home teams that have won the first two games of a best-of-seven postseason series have gone on to win the series 80.8 percent of the time — though one of the few teams to dig out of a World Series 0-2 start was the 1986 Mets).
Meenan knows that it is easy to cheer for the team now, during a largely successful season, but he is grateful that his company's beginnings came during hard times. "It's good for the sport, and it makes people more passionate and brings the fire back, win or lose," he said.
This story has been updated to reflect the fact that New York Mets player Curtis Granderson recognized The 7 Line Army at a game in Baltimore, and the Yankee Stadium visit was the third annual "Bronx Invasion."
—By Michael Sheetz, special to CNBC.com