The fifth season of "Deep Space Nine" marks a turning point for the show. The Klingon faction instigated by Worf's arrival is occasionally played for laughs, but mostly, their hardheaded personalities foil all diplomatic efforts. Expanding on the new theme of duplication, the crew makes several trips to their mirror-universe counterparts, and Sisko (Avery Brooks) and crew get to interact with Captain Kirk and Spock in the "Tribbles" episode.