Asked by director Frank Coraci to polish the script, Carrie Fisher spent six months on it, making it her special mission to add "heart and strength and dimension" to the Drew Barrymore character, Julia. Thereafter, when she was asked what her secret sauce was for script doctoring, she'd reply: "Make the women smarter - and the love scenes better."
The butterfly jean jacket that Julia wears throughout the movie belongs to Drew Barrymore. Director Frank Coraci liked her jacket and told her to wear it as part of her costume.
Robbie tells Linda at one point to "Get out of my Van Halen t-shirt before you jinx the band and they break up." David Lee Roth left Van Halen in 1985 (the year in which the movie is set) so one can assume Robbie's prediction is half right.
Although Steve Buscemi's and Jon Lovitz's appearances in the film are uncredited, at the soundtrack section on the end credits the songs "True" and "Ladies Night" are marked as "Performed by Steve Buscemi" and "Performed by Jon Lovitz" respectively.