"The Ghost and Mr. Chicken" centers on Don Knotts playing a small town ne'er do well, Luther Heggs, who is dared into spending the night at a haunted house. The film was a hit on its release in 1966 (via TCM), and features a recurring joke that became a phenomenon outside the original source. When Heggs especially embarasses himself in public, an offscreen character yells, "'Attaboy, Luther!"
According to TCM, Andy Griffith, Knotts' co-star on "The Andy Griffith Show," came up with the line while working on the script in an uncredited role. This became a popular quote (via TCM) in the culture at the time, with the studio even using it in promotional material for the movie. The Farrelly Brothers eventually also found a way to work the phrase into their own comedy.
During the climax of "Kingpin," Munson gets ready to make another move against McCracken in the tournament. As he steps up to bowl, someone shouts, "'Attaboy, Luther!"
It hasn't been confirmed if the nod was intentional, but the Farrelly Brothers are definitely big fans of "The Ghost and Mr. Chicken." The two even called Knotts' performance one of their favorites in a 2007 interview with Cinema Blend. Either way, it's one great comedy paying homage to another.