According to Neil Patrick Harris' autobiography, the "missing girl" on the milk carton in one scene is actually a picture of Alyssa Milano.
The movie was filmed in 1986 but not released until two years later.
"Clara's Heart" was the final big-screen film produced by MTM Enterprises. When it was originally released, the company had already been purchased by the Television South (TVS) Corporation of London, England. The MTM empire would be in business for just nine more years, after which it was purchased by 21st Century Fox, Inc. (then doing business as NewsCorp) and absorbed into 20th Century Fox. However, Warner Bros., which co-produced and originally distributed the film, still owns it (WB owned the greater share of the production).
In a 2018 taping of "The View," Neil Patrick Harris said that Whoopi Goldberg approached him on the last day of filming and told him she planned to have sex with him in ten years' time. Goldberg tacitly acknowledged making these remarks but claimed they were in jest. Harris was 14 at the time of filming and Goldberg was 31.