Frost was a chain smoker in the novels. In his 2013 autobiography "My Life" David Jason revealed they decided to make Frost a non-smoker in the television series as he had recently quit smoking cigarettes in real life.
In a 2008 interview David Jason admitted he had to stop playing Frost because he was too old to play a policeman.
Arthur White, who plays Ernie Trigg, is David Jason's real life elder brother. There was already an actor called David White registered with the acting union so David chose to use Jason as his stage name.
David Jason grew a moustache for the role. It was his idea, as he imagined Frost grew one in his youth to give himself a few extra years and more maturity. He lost the moustache between series to play other parts and than needed four weeks to grow it back as well as stop shaving at the right time ahead of shooting. Sometimes Jason missed the mark and had to help it along with a bit of "coloring-in"' but it was always ready for filming.
Novellist R.D. Wingfield, whose "Frost" book were the inspiration for the series, was very critical of the TV adaptation and said that it had ruined the character of Jack Frost that he had created in his novels.