Continuity mistake: Charlie, Olivia's former partner and friend in the FBI shows up in this episode during the interview with Mrs. Rusk, but Charlie was killed off by one of the shapeshifters in a previous episode, and the shapeshifter that killed Charlie was himself killed off by Olivia, who in other episodes reflected back on killing him. This episode was supposedly meant to be in season 1 as ep 21 or 22. Unknown why they didn't air it then, and decided to put it in the middle of season 2 (for no apparent reason).
Other mistake: The battle droids - including the commando droids featured here - habitually have two broad fingers and a thumb. So how can a commando droid squeeze itself completely into clone trooper armor without its broad fingers tearing open the gloves, since it can't separate its fingers?
Continuity mistake: All shots of the Jeep Cherokee prior to it crashing (and during the process of flipping over) show that it wears factory-optional silver steel wheels of a 'star' style. But as the wreck settles upside-down, it's wearing plain steel wheels (like those found under full wheel covers or on a spare tire).
Continuity mistake: During "Brand New Day", at one point, Dr. Horrible stabs a picture of Captain Hammer attached to a dartboard with a handful of darts, all right in the center of the picture. A few shots later as Dr. Horrible sits, suddenly the darts are far-more spread out. (It's in the background and can be hard to see, but it's noticeable.)
Triumvirate of Terror! - S3-E8
Continuity mistake: Cheetah slams Superman into what looks like a computer mainframe. He stumbles forward and falls to his knees. The next shot as Cheetah kicks him, he is suddenly standing again and in the middle of the room, away from the mainframe. (00:12:55)
Audio problem: They went to an investigator to let him listen to the audio. The audio with the woman screaming and the gasp, the gasp was Zak, not another apparition.
Other mistake: When the team is in the grocery store, they rewind the security videotape (they play it backwards). They stop it at the last activity, when a man comes in and chainsaws his own head off. The body (and head) have gone blue/purple, and since everyone else died the previous night, we can assume that he cut his head off around 12 hours ago. At high speed reverse play, the time they spent rewinding would be only around 10 or 15 minutes of recorded time. (00:32:50)
Continuity mistake: When Wolverine opens the door and Emma Frost is there, she is within less than an arm's reach of the door. When she says she has decided to join the X-Men, she along with Wolverine and Angel are suddenly a few steps outside away from the door, even though she was never shown stepping back. (00:02:17)
Containment - S1-E5
Continuity mistake: At the end of the episode, when the bad guy is preparing the syringe of small pox, he follows the usual method of tapping out any air in the tube - when he is shown injecting himself, a large air bubble is back in the syringe (which would probably kill him quicker than the smallpox).