At the Ministry of silly names. Miss Franny was about to start work and the Director decided he should gather the staff together to introduce her. Her name amused him and before the introduction he said to himself, over and over again "I must remember the 'R' I must remember the 'R'"
When the time came to introduce her he actually remembered the 'R' but his introduction did not go quite right! Having forgotten her actual name, he introduced her as miss 'Prussy'