Continuity mistake: In Season 2's episode "The Yellow Peril" we see the boys' mum's grave. However in this episode the layout and surroundings have completely changed. (00:05:15)
Continuity mistake: When Del is going on about the plastic surgeon in Rodney's screenplay, the way he holds the bottle of drink keep changing through instant cuts. (00:19:50)
Continuity mistake: In 'The Frog's Legacy' (1987), Del & Rodney learnt the story of Freddy The Frog for the first time - neither of them had ever heard of him before (Aunt Irene explains to Del who Freddy was. She mentions both 'Freddy The Frog' and his real name 'Frederick Robdal'. Del has heard of neither of these names). Yet in 'Sleepless in Peckham', it would seem that Del had known Freddy since he was 15. He even went on their first Jolly Boys' Outing with the rest of the gang.
Continuity mistake: In one episode, Del tells Rodney that he was born 13 years after him. Yet in this episode, when looking at the picture, Rodney says that Del is 15 and that he hadn't been born at the time the picture was taken.
Chosen answer: An apparent long string of illnesses.