At the beginning of the movie, when the twins are getting out of bed, there is a shot that shows their feet on the floor and there appears to be a face under the bed. It's rumored to be baseball equipment, but is actually the executive producer, hiding to see if the director would notice. He didn't.
Ben Carson is an actual doctor who has successfully separated conjoined twins in real life. In a 22-hour surgery, he was the first doctor in history to accomplish this task with both of the twins surviving. His wife and three children also appear in the hospital waiting room.
Ray 'Rocket' Valliere's speech following the credits was not planned. He rambled on while the cameras kept rolling. Lunch had already been called and the crew was restless. But his speech was so heartfelt that no one stopped him.
When Cher first signed on to do the movie, the character in the script she was supposed to play just said "actress". Peter Farrelly and Bobby Farrelly thought it would be a cool idea if Cher just played herself, and so they changed it.
In the homecoming game scene, the twins trounce the Nantucket Whalers while playing for the Martha's Vineyard Vineyarders. There is a very close rivalry between both high school football teams and many people from Martha's Vineyard were delighted to see the Whalers lose on film. Nantucket had no comment.
The eclectic way in which Greg Kinnear sings "Summertime" near the end of the movie is a very close imitation of the way late soul singer Billy Stewart sings the song on his "Unbelievable" album, released in 1966.
The trivia item below may give away important plot points.
To date, no separation has ever been performed on adult conjoined twins with both twins surviving the operation. So far, the oldest twins to successfully undergo the procedure were conjoined Utah twins Kendra and Maliyah Herrin, who were 4.5 years old when they were separated on 8 August 2006. In a case of life imitating art, one of the first things Kendra said upon regaining full consciousness was, "Why isn't Maliyah stuck to me anymore?"