Penelope Farmer was born in 1939 in Kent. She was a twin, although doctors weren't aware of her existence until she was born twenty-five minutes after her sister was born. Many of Penelope's novels deal with the issue of identity and some readers suggest that this is because she is a twin. In Charlotte Sometimes the strange things that happen to Charlotte force her to question her own identity and ponder the possibility that it could be lost.

Penelope Farmer has written many books for both adults and children in the course of her long career as a writer. Charlotte Sometimes is actually the third book in a trilogy featuring the characters of Charlotte and Emma Makepeace. Penelope currently lives on the Spanish island of Lanzarote, one of the Canary Islands, and writes a blog under the name Granny P.