The scene where Rodney sprinkles Del's aftershave over Albert's kipper was done without telling Buster Merryfield. Thus, his reaction to the kipper's aftershave taste was genuine. Reportedly, Merryfield was initially irritated by this.
When Rodney is writing down the list of newspapers and TV companies that Del is giving him over the phone, he mentions Channel 4 but Del obviously says no and Rodney then agrees.
This is because in its early years Channel 4 was not a commercial success and therefore, was the butt of many jokes.
The idea for the script goes all the way back five years earlier to "The Second Time Around (1981)", where Grandad told Rodney about how Del used to donate to the church roof fund.