The character of "Troy Gable" is based on director Sean McGinly's experiences as road manager for The Amazing Kreskin, on which The Great Buck Howard is loosely based.
Kevin Kline was originally going to play Buck Howard. Colin Hanks stated this in an interview at the premiere of Zathura: A Space Adventure (2005).
The way Buck Howard finds his check at the end of his show, is not the way The Amazing Kreskin (on whose career the movie is loosely based) used. The method was depicted differently, probably for dramatic purposes.
The Las Vegas scene was filmed in Hollywood on the same set that was used for the Palace Hotel Ballroom scene in Blues Brothers (1980).