Steve Young, who played professional football for the San Francisco 49ers (among other teams), plays "Bro. Niner." During his scene in the film, Bro. Niner quotes Brigham Young--of whom Steve Young is a direct descendant.
Sam (played by "Jeremy Elliot (I)") is seen reading the book "Charly". Elliot starred as the male lead Sam Roberts in the movie version of said book.
Wally Joyner, who played professional baseball for the California/Anaheim Angels (among other teams), plays "Bro. Angel."
While performing for students at the University of Missouri, Jonathan tells the crowd where his car is parked so that they can "steal all of (his) stuff" and burn it to the ground. This comment refers to the infamous "Extermination Order" against the LDS (Mormon) Church, issued by Missouri Governor Lilburn W. Boggs on October 27, 1838. This order called for the Mormons to be driven from the state or wiped out. (It was not formally repealed until 1975.)