Deliberate mistake: Old Weird Harold's pants fall down twice in the film. His boxers are different colors each time; once they're red, the other time they're blue. The director admits to this deliberate mistake in the commentary, siting his interest in seeing if people will notice.
Deliberate mistake: Fading is mentioned throughout the film. However, according to the director in the commentary, they don't really start to fade until the third time it's mentioned.
Answer: He has said in many interviews that they were based on his friends growing up. The characters of Bill and his little brother Russell, were Bill Cosby and his brother Russell. Thou the adventures were exaggerated, the characterizations were real.