Anthony Michael Hall and Molly Ringwald initially disliked each other, so John Hughes took them to a record store and they bonded after they found out they like the same music. One of the groups they liked was The Rave-Ups which Molly scribbled on Samantha's notebook.
The movie's costume designer begged Molly Ringwald not to wear the hat she wore in the beginning of the movie. Ringwald insisted. After the movie was released, teenage girls started wearing their hats tilted back like that.
Carlin Glynn (Brenda) confronted John Hughes about the fact that the script didn't call for her to apologize for forgetting her daughter's birthday, despite the fact that her character was described as a good and attentive mother. Hughes agreed, and added the scene where Brenda tearfully apologizes to Samantha (Molly Ringwald).
Of all the films Molly Ringwald made with John Hughes, she said, "I had the most fun on Sixteen Candles."
Haviland Morris didn't want to do the shower scene, because the point was that she had bigger breasts than Sam and Randy, which she didn't. So they had a body double for her.
Dick Biondi: Chicago radio legend is heard on the radio (uncredited) in the opening bedroom scene where Molly Ringwald is looking in her mirror.