The actress was cast based on her sole audition without performing a screen test. Although Marshall believed that several other actresses seemed capable of embodying Mia's comedic aspects, he determined that only Hathaway possessed "the grace and authority" to deliver the character's final speech. Hathaway identified with her character's struggles and personality, explaining, "Mia was very similar to the person I was in high school", describing herself as a wallflower to whom few paid attention and appreciating the opportunity to be herself in a film. Hathaway's appearance and performance reminded Marshall of Julia Roberts, whom he had directed to great success in the romantic comedy "Pretty Woman" (1990), describing her as a fusion of Roberts and comedian Harpo Marx due to her combination of glamour and physical comedy, which he also likened to his own sister Penny Marshall. Hathaway gained weight for the role to closer resemble "a regular teen". The actress credits Marshall with teaching her the most important lesson of her career: "You never know what's going to be a hit, so you might as well have fun making it."