The Tantalus Device Mirror used in Star Trek and Mission Impossible episode Encore (S6, E2) appears again in Margaret's Bedroom.
This episode is the first produced of season 7, and the first appearance of Greg Morris's mustache. According to the actor, he decided to grow it for no particular reason. However, there's a speculative notion that the mustache might have been a deliberate diversion, possibly intended to shift viewers' attention away from Lynda's pregnant body.