Talia Shire's performance as Adrian was one of the hidden strengths of the original Rocky that allowed it to become such a big hit and start a franchise that continues to this day, but Shire wasn't the first choice for the part. In a 2010 interview with Ain't It Cool News, star Sylvester Stallone lists a quartet of actresses who were originally considered for Adrian. The list gives an interesting look into how different Rocky could have been if the creators had gone with their first instincts.
The first name considered for Adrian was singer and actress Cher. At the time, Cher was perhaps best known as the star of the highly-rated variety series The Sonny & Cher Comedy Hour and her own solo series Cher, and her only dramatic acting appearance had been in the 1969 self-financed flop Chastity. Only in the 1980s would Cher, who almost starred in a Mad Max film, fully demonstrate her acting skills in movies like Moonstruck and The Witches of Eastwick. Appearing in Rocky could have jump-started her acting career, but the presence of a recognizable music and TV star could have disrupted the first movie's realism.
Another name that made the shortlist to play Adrian was Bette Midler. In the mid-1970s when Rocky was coming together, Midler was still a Broadway actor and singer, and wouldn't make her film debut until 1979's The Rose. The boxing drama would have been an auspicious debut, but ultimately Midler turned it down, and it's difficult to imagine Midler's theatrical persona gelling with the role of shy Adrian in Rocky.
Susan Sarandon was also in consideration to play Adrian, according to Stallone. Sarandon was at that time best known for her appearances in soap operas and The Rocky Horror Picture Show. Sarandon would later go on to much more acclaim as an actress, including four Academy Award nominations and one win. Adrian would have been a more subdued character than Sarandon typically plays, but she could potentially have made it work.
The final name that Rocky alumnus Stallone mentioned as a casting choice was Carrie Snodgress. Snodgress was Rocky director John G. Avildsen's first choice for Adrian, as the character was originally written to be of Irish heritage with a brother played by Harvey Keitel. Snodgress was, at the time, the most established actress of the quartet, being already an Oscar nominee. She reportedly turned down the role due to low pay. Avildsen would cast Snodgress in two movies later in his career.
Like Rocky star Sylvester Stallone, three of the four actresses mentioned above were at the start of extensive careers that would see them become much more recognized, a tribute to Avildsen's eye for talent. Ultimately, all four turned the movie down, and Talia Shire instead got the role based on an audition just days before filming began. Shire's portrayal of Adrian as an uncertain, mousy pet shop clerk stood out from the expectations of Hollywood love interests and helped make Rocky's story feel grounded and unique. Shire would go on to portray Adrian in four Rocky sequels. The original casting ideas for Adrian provide an intriguing idea of how different the movie could have been with an alternate lead actress but, as Stallone says, ultimately show that "sometimes initial failure is good and leads to an unexpected outcome."