The names of the main characters: Rich, Amy, and Mr. Morris are all references to the concepts money, love, and death. The theme of each one of their days doesn't correlate with their name, however, if you reinterpret the characters - Rich is the richest person in the movie, Amy is the object of love, and Mr. Morris is slowly killing himself.
Thing 1 and Thing 2 are originally Dr. Seuss characters. The writer chose these names, however, after listening to Nirvana's Unplugged album.
The concept of Daze originated when the writer/director Jeff Dean and a few friends dressed up as Elvis with for Halloween. He noticed that everyone treats you differently when your dressed as Elvis, which intrigued him.
The original choice for the Delivery Man didn't show up that day so Charles Anthony, a PA on the production was given the part.
Originally the dildosizer pitch was about personalized dildos until the writer found out they already existed.