Update: Jeri Ryan contacted Screen Rant with the correction that the problems she encountered involved her Borg drone costume and not her catsuit. The original article is as follows.
The skintight catsuits worn by Seven of Nine on Star Trek: Voyager are unforgettable, but her original silver costume had to change because of the numerous problems it caused for actress Jeri Ryan. Seven of Nine debuted at the start of Star Trek: Voyager season 4, and Seven literally became the face of the Star Trek spinoff. Seven appeared on numerous magazine covers while Ryan repped the series with appearances on talk shows. Of course, Seven's striking beauty and sex appeal were a prime reason for her popularity.
Seven of Nine was created by Star Trek: Voyager executive producers Brannon Braga and Joe Menosky; Braga became fascinated with the idea of a Borg character coming aboard the Captain Kathryn Janeway's (Kate Mulgrew) starship, but it was producer Rick Berman who suggested they make their creation into "a Borg babe." While Braga's vision of Seven of Nine was "a wild child... a girl raised by wolves" who would inject conflict into the U.S.S. Voyager, the producers agreed with Berman that Seven would also inject some sex appeal into the series, which had suffered falling ratings ever since its splashy January 1995 debut as the flagship series of the United Paramount Network (UPN).
Of the actresses who auditioned, Jeri Ryan's combination of brains and beauty made her the best choice to be cast as Seven of Nine and the actress instantly knew what was expected of the character when she saw her initial costume. Although Seven is introduced as a Borg drone, once she is "reclaimed" by the Voyager crew and returned to her human form, Ryan donned Seven's infamous skintight silver catsuit. Ryan wore the silver suit for a few episodes, but it was retired because of the many issues it caused for the actress. The catsuit, with its corset complete with molded breasts, was so restrictively tight that Ryan had trouble breathing. In fact, nurses with oxygen tanks were present on the set and Ryan passed out four times during production. In addition, not only did the corset prevent Ryan from bending but it took her 20 minutes to go to the bathroom, and production would need to be halted just so the actress could relieve herself.
The silver catsuit with the high collar, of course, is what Ryan wore as Seven of Nine in publicity photos for Star Trek: Voyager, but the actress spoke up about her discomfort and her uniform was changed. Less restrictive (but no less form-fitting) alternate costumes were designed in various colors. A brown costume had no collar, which allowed Ryan to turn her neck, and throughout the four seasons she starred in, Seven rotated between cobalt blue, grey-blue, and plum-colored versions of her catsuit. The in-universe reason for Seven's initial catsuit was that the fabric helped her skin regenerate after many years as a Borg drone, but Seven's sex appeal became an indelible part of the show so the catsuits stayed. Seven did get to wear a Starfleet uniform on two occasions, however.
Naturally, Seven of Nine was a lightning rod of controversy and she was accused of being eye candy to pull in male viewers. Ryan was matter-of-fact that this was indeed the case. She told TV Week in 1999, "I knew exactly what I was in for when I had my first costume fitting. Clearly, my character was added to the show for sex appeal, which remains the one way to get attention very quickly. I don't think it's the only way to get viewers to watch strong women, but it worked."
Seven of Nine's sex appeal certainly wasn't an outlier in terms of the overall Star Trek franchise. There was plenty of blatant eye candy in Star Trek: The Original Series and Counselor Deanna Troi (Marina Sirtis) wore form-fitting costumes on Star Trek: The Next Generation. There's no doubt that Star Trek: Enterprise's producers were motivated to duplicate Seven of Nine's bombshell status with T'Pol (Jolene Blalock), who also wore skintight catsuits and was even more sexually provocative. Still, Seven of Nine earned the respect of fans for her cool intelligence as well as her looks and, in Star Trek: Picard, Jeri Ryan left the catsuits behind in her comeback as Seven of Nine.