Penned by James Roday, the hour-long finale, which is titled "A Nightmare on State Street," will also feature guest stars Billy Zabka, Brie and Nikki Bella, Bruce Campbell, Dean Cameron, Phylicia Rashad, Kurt Fuller and Mira Sorvino.
Foster, most recently seen in the now-canceled "Bunheads," will play a middle school teacher. The episode, Deadline.com reports, will follow "a sleep-deprived Gus into dream therapy as he attempts to get to the bottom of recent night terrors. After his treatment, however, nothing is what it seems, and he soon learns that 'in dreams, no one can hear you scream!'"
Foster will play New York's Café Carlyle Sept. 10-28.