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Mars Attacks is the third episode of the seventh season of ER, and the one hundred thirty-ninth episode overall.
Guest Stars: Ellen Crawford (Lydia), Troy Evans (Frank), Alex D. Linz (Dennis), Laura Ceron (Chuny), Lily Mariye (Lily), Kyle Richards (Dori), Jorge Luis Abreu, Rebecca Balding (Mrs. Garvey), Christine Cavanaugh (Gloria), Kevin Durand (Mr. Mooney), Jamie Marsh (Mr. Kamatovik), Khandi Alexander (Jackie), Elizabeth Mitchell (Dr. Kim Legaspi), Lynn A. Henderson (Olbes), Demetrius Navarro (Morales), Nynno Ahli (Security Guard), Michelle Bonilla (Harms), Duffy Epstein (Griffin), G. Adam Gifford (Pelvis Man), Steve Hanneman (Patient), Bradley James (SWAT Guy), Brian Lester (Dumar), Aaron Pruner (Alien Boy), Devon Reeves (Moira), Charlie Stewart (Albert), Eric Stonestreet (Willie), Toshi Toda (Japanese Businessman #1), Craig Tsuyumine (Japanese Businessman #2), Ludo Vina (Lupe), Emily Wagner (Pickman), Claudia Michelle Wallace (Parking Attendant), Chris Warren (Boyfriend), Matthew Watkins (Reese)
Carter returns to work after completing his drug rehab and cares for a handcapped boy with a bladder infection; the ER is filled with patients after a beam collapses during a sci-fi convention and Corday talks Mark through a complicated procedure on one of the patients; Romano fires Benton over the EMTLA violation; Weaver has Abby return to the ER to work full-time as a nurse; Frank annoys the ER staff when he runs background checks on the patients.