"Maybe that will make me sound more believable when I say that you are not in a simulation," Tali says. Of course, the visitor could attribute the failure of his override to some kind of serious malfunction, and try something else: Tali certainly would, were she in his place. And it's not like the Enterprise holodeck hasn't had some crazy-weird malfunctions before. "There's no reason for alarm, though. Milliways is safe."