Shortly after the film's release, New Zealand Police reported an increase in Mini thefts across the country.
Most of the audio for the chase scenes had to be re-recorded in post-production. This was due to the noise made by the numerous gravel roads.
The beginning title card mentions driving your car whenever you pleased. This is a reference to 'car less days' that were introduced by the Muldoon government in 1979. With car less days, unless you had a exemption, you were not supposed to drive your car on the day of the week displayed on your windscreen or you could face a hefty fine. Ironically, they were phased out before Goodbye Pork Pie even reached the cinemas.
While John and Gerry are in the tearooms, the television news announces the death of Pope John Paul I. This would date the film to occur around 28 September 1978.
In one scene, John and Gerry visit Cromwell and sell the steel trim, grille and batter, and take an oil can at a garage before driving over a bridge. Where this scene takes place was later flooded in 1992-93 by the creation of Lake Dunstan as part of the Clyde Hydroelectric Dam scheme. The garage was demolished and the bridge is now under 10 metres (33 feet) of water.