Miss Clare's Family (which was the eldest sister, and what happened to her brother?)
Historical Errors (books that contradict information in earlier books)
Crossword Clues (those ubiquitous dairycats)
Changing Names (is it Alfred George or Bob?)
The Children that Never Age (Joseph, Ernest, Patrick, etc, who have been at school since 1955)
Merging Characters (twins absorbed into the Coggs family)