Roddy McDowall - born September 17, 1928 - was 36 years old, playing a high school senior, when this movie was filmed in 1965 for its February 21, 1966 release. Roddy played opposite a 22 year old Tuesday Weld, but was the same age as Harvey Korman (as the school principal) and only 3 years younger then Lola Albright (Weld's mother).
Tuesday Weld told film critic Rex Reed that this was her favorite film and that she thought she gave her best performance in it.
Barbara Ann's sweaters as mentioned in chronological order: Grape Yum Yum, Banana Beige, Lemon Meringue, Pink Put On, Papaya Surprise, Periwinkle Pussycat, Turquoise Trouble, Midnight A-Go-Go, and Peach Putdown.
This film took nearly eighteen months to get to Britain and was shown (in an abbreviated version) in the lower half of a double-bill with "A Fistful Of Dollars". It was not press-shown or given much publicity, but the popularity of the Clint Eastwood film meant that it was widely seen, and it gradually built up a cult following. It was eventually televised in its full version.
Larry H. Johnson, listed as George Axelrod's co-writer on the film, was newly out of film school when he was hired; Axelrod claimed he thought of Johnson as "a kid we can exploit" when hiring him. He has had no other writing credits in films or television since.