Lane Bradbury, who plays Sally Field's younger sister, is actually eight years older than Sally--a testament to the versatility of both actresses.
The backyard and pool was also used in The Graduate".
The hippie-shack window Flack crashes through was actually a false wall (with window) built in front of the garage at the home used as the Miller's house. Slowed way down, the white stucco house across the street can be seen momentarily as Flack hits the ground.
Sally Field plays Eleanor Parker's daughter here, in Home for the Holidays (1972) (TV) they play sisters.
According to Sally Field's memoir, the first draft of the script was written by Steven Spielberg.