In 2001, she made a brief appearance in the horror movie Jeepers Creepers, and the following year starred in the dark comedy film Comic Book Villains, with DJ Qualls. In recent years, Brennan had guest-starred in television, including recurring roles as the nosy Mrs. Bink on 7th Heaven and as gruff-acting coach Zandra on Will & Grace. In 2003, director Shawn Levy cast her in a cameo role of a babysitter to Steve Martin and Bonnie Hunt's children in an updated remake of Cheaper by the Dozen. Levy was inspired to cast Brennan after seeing Private Benjamin on television. However, Brennan's cameo was deleted from the actual cut of the movie. Nonetheless, she did receive credit for her role on the deleted scenes special feature of the film's DVD. In 2004, she appeared in the horror film The Hollow as Joan Van Etten. That same year, Brennan was nominated for an Emmy for her performance as Zandra, Jack McFarland's caustic drama teacher, on Will & Grace.