^Yeoman Smith was played up in that brochure and other publicity as being the third lead, part of the core trio with Kirk and Spock, but she ended up having exactly one line, "The name's Smith, sir." Plus that non-dialogue bit where she was scared and Mitchell held her hand. Otherwise, her entire purpose in the pilot was essentially decorative.
When Gene Roddenberry was asked about this non-part, he allegedly said : "I only hired her because I wanted to score with her."
He must have wanted that score pretty bad to promise her third lead