
Japp is mentioned by Poirot in Death on the Nile (1937), and by Colonel Weston in Evil Under the Sun (1941), the next book in the Poirot series after his final appearance.

In chapter seventeen of The Murder of Roger Ackroyd (1926), Japp is mentioned by a police superintendent to Poirot as having asked after him. Inspector Japp is also briefly mentioned in the Tommy and Tuppence book The Secret Adversary (1922) his card is brought to Julius Hersheimmer at the end of chapter five.

In number of appearances, Japp is comparable to Arthur Hastings who was featured in eight of the Poirot novels. He returns in this capacity in Death in the Clouds and One, Two, Buckle My Shoe, before being written out of the series. However, Japp emerges as a major character and partner to Poirot in Lord Edgware Dies. In most of these appearances, Japp is a minor character with minimal interactions with Poirot or involvement in the plot. This is his last appearance in any work by Christie. One, Two, Buckle My Shoe (1940), also known as An Overdose of Death and The Patriotic Murders.Murders (1936), also known as The Alphabet Murders Death in the Clouds (1935), also known as Death in the Air.Lord Edgware Dies (1933), also known as Thirteen at Dinner.Japp has been depicted in seven novels written by Christie, all featuring Hercule Poirot: In the first novel in which Japp appears, The Mysterious Affair at Styles, he is described as a "ferret-faced man", which is similar to the description of Lestrade as a "ferret-like man" in Doyle's 1891 short story " The Boscombe Valley Mystery". Christie even modelled Japp after the "ferret-like" qualities of Lestrade. Inspector Japp was inspired by the fictional police detective Inspector Lestrade from the Sherlock Holmes stories by Arthur Conan Doyle. Inspector James Japp (later Chief Inspector Japp) is a fictional character who appears in several of Agatha Christie's novels featuring Hercule Poirot. Philip Jackson as Japp in Agatha Christie's Poirot
