The movie includes the house where Karen Carpenter died in real life, and the real-life ambulance and paramedics who were on the scene.
Cynthia Gibb performed just one song, "The End of the World." She lip-synched all of Karen Carpenter's other songs.
Much of Cynthia Gibb's wardrobe was made up of Karen Carpenter's actual clothes, which her family had kept. At the same height, and with roughly the same (pre-anorexic) figure, the clothes fit, and wearing them helped Gibb get into character.
Lucy and Karen are backstage before a show and Lucy excitedly exclaims, "The rabbit died!" During the mid-twentieth century, "the rabbit died" was a euphemism for pregnancy. The origin of the phrase was the fact that the first reliable pregnancy test involved injecting the possibly pregnant woman's urine into a female rabbit and then examining the rabbit's ovaries to see if they showed a response that only occurred when they were exposed to a hormone secreted by pregnant women. The phrase led to a widespread misconception that the rabbit only died during the test if the woman was pregnant, when in fact the rabbit died either way; the only way to examine the rabbit's ovaries was to kill it.