In season 1 when Meadow is messing with Tony asking "Who invented the Mafia?" She mentions the Five Families and Luciano as the inventor of La Cosa Nostra, but identifies the Families as "Lucchese, Gambino, Bannanno, Profaci" never mentioning the 5th. Paulie brings up the Columbos later on when they're talking about taking out Phil Leotardo. "I lived thru the 70's by the skin of my nuts when the Columbos were goin' at it." Which I don't really get because why would Paulie have anything to do with an internal war in the Columbos? I know he was an associate of them in real life. They mention John Gotti and Sammy Gravano a couple times on the show. When they have the sit down where Butch gives Tony the OK to take out Phil, it's brokered by a "semi-retired" George Paglieri, Boss of the Paglieri Family.