Revealing mistake: (Part 4) After Omega takes off his mask and looks in the mirror, when he sees that his physical body doesn't exist he puts his mask back on and screams, but when he shouts, "If I exist only by my will, then my will is to destroy," Omega's mask pops up off his face, and we can see the actor's blackened face as he shouts the last bit of his dialogue. (00:07:10)
Continuity mistake: In flashback, we see the one-armed man kill Helen Kimble by striking her with a heavy lamp. All through the earlier seasons, though, we were repeatedly told that Helen had been strangled. (00:28:50)
Deliberate mistake: During the 6/11/04 episode, Jax and Courtney are having dinner in Italy. Carly, who is in New York, does some sleuthing, finds out where Jax and Courtney are, and flies to Italy. Miraculously, Carly manges to fly from New York to Italy and arrive while Jax and Courtney are still eating dinner.
Continuity mistake: When the lab equipment shorts out after the earthquake, the unconscious Major Brothers is lying with his head propped up against the wall. But when Hamilton reaches him in the next shot, he's suddenly lying flat and is nowhere near the wall. (00:21:45)
That Little Old Matchmaker, Martin - S1-E12
Character mistake: In Bill's office, after Tim talks about the acoustics in the building, Bill calls Tim "Bill." (00:15:51)
Who Killed Avery Lord? - S1-E23
Visible crew/equipment: After the woman in the negligeé goes back into her apartment, a crew member's shadow appears on the corridor wall. (00:42:00)
Revealing mistake: Patty Duke's stand-in is visible behind Cathy when the family is in the front hall welcoming their aunt.
Betty Jo's First Love - S1-E23
Visible crew/equipment: While Billie Jo and Bobbie Jo are dancing with their dates, when Betty Jo stands up and tries to get Orville's attention, the shadow of the moving boom mic is visible at the top, right corner of the screen. (00:19:05)
Factual error: They show a clip of a kamikaze diving into a ship. The clip they show was actually an event from much later in the war: offshore of Okinawa. No ship on either side was struck by a plane during the Battle of Midway.