By Brian Lowry, CNN

(CNN) -- Penny Marshall crammed a lot of creativity into a relatively concentrated period, from her iconic sitcom work to her transition into directing, producing an iconic TV show and a memorable string of movies.

Marshall, who died Monday at age 75, left her mark both in front of and behind the camera. Her older brother, producer and director Garry Marshall, was certainly instrumental in her TV stardom, casting her in "The Odd Couple" (as Myrna the secretary) before she landed on "Happy Days" and eventually her own wildly popular spinoff, "Laverne & Shirley."

Still, Garry was quick to reassure his sister that nepotism wasn't responsible for her good fortune. In a 1988 interview, Penny told the Los Angeles Times that her brother had said, "'I'm not giving you a job 'cause I'm nice. I'm not that nice.'"

Marshall's gifts as a comic actress turned out to be the most recognizable aspect of her career, but not necessarily the most impressive. Having directed a few episodes of "Laverne & Shirley," she had the opportunity to direct "Jumpin' Jack Flash," a 1986 comedy starring Whoopi Goldberg.

The movie failed, but it opened the door to the film world, which paid off with "Big," the whimsical comedy-fantasy starring Tom Hanks. That box-office hit made Marshall the first woman to direct a movie that earned more than $100 million.

Marshall followed that with "Awakenings" -- a moving drama starring Robert De Niro and Robin Williams -- before reuniting with Hanks on "A League of Their Own," the popular baseball movie that made its debut in 1992.

Marshall directed three more movies over the next decade ("Renaissance Man," the remake "The Preacher's Wife," "Riding in Cars With Boys"), then shifted to episodic TV work and occasional guest appearances. But in hindsight, her career was largely defined by what amounted to a staggeringly creative 20-year stretch beginning in the mid-1970s, bookended by the premiere of "Laverne & Shirley" and the release of "The Preacher's Wife," which starred Denzel Washington and Whitney Houston.

In interviews, Marshall often talked frankly about her insecurities, including her concerns early in her career that she wasn't pretty enough to succeed as an actress. "I grew up believing an actress is supposed to be beautiful," she once said.

At the same time, she was immersed in show business, having been married to actor-director Rob Reiner (they later divorced) in addition to her frequent collaboration with her late brother, which included narrating his final film, "Mother's Day," and guest starring in his "The Odd Couple" series revival, both in 2016.

To paraphrase the "Laverne & Shirley" theme song, Marshall might not have made all her dreams come true. But her self-confessed doubts notwithstanding, she left behind a big, beautiful screen legacy.