The Killer - S1-E1
Continuity mistake: At the beginning of the episode, The Killer (John de Lancie) strikes. He is holding the champagne flute with the middle finger curled between the hand and the belly of the glass, but in close-up the finger is at a right angle in front of the stem. (00:01:55)
The Killer - S1-E1
Continuity mistake: Jim's pupil and successor Copperfield is poisoned at the beginning of the episode. He screams, drawing the attention of the party guests. In the following POV shot, the guests are standing in entirely different spots in the room all of a sudden. (00:02:45)
The Killer - S1-E1
Revealing mistake: When Copperfield meets an untimely demise, Vince Martin' s stunt double that performs the fall is recognizable as such (his hair does not even remotely match). (00:03:25)
The Killer - S1-E1
Continuity mistake: When Jim picks up the box with the mission briefing, his hand in the close-up of the fisherman's case is at the bottom of the box, but it's on the opposite side when we see Peter Graves retrieve it. (00:07:00)
The Killer - S1-E1
Revealing mistake: When Drake puts the bomb against the ceiling, the 'concrete' wobbles. (00:40:00)
The Killer - S1-E1
Other mistake: We are of course not privy to the protocol of the secret service organization Jim Phelps is a member of; however, while he is at his own place choosing at his leisure the team members, Jim to pick Nicholas types "KJ" on the laptop, to pick Casey he types "PK", then to pick Max and Grant he just clicks a TV remote. Whatever system they are using, does not seem to make any internal sense.
The System - S1-E2
Continuity mistake: Jim approaches the secret agent on the usual convoluted way to the mission briefing. The peanut vendor mentions the quarterback, and behind him there is a person walking in the tunnel. Switch to a new shot and there are two. (00:02:40)
The System - S1-E2
Visible crew/equipment: Jim Phelps gets the disk system from the locker. He then takes a step back and looks around the room figuring out where to sit to play the recording. As the camera moves to follow, a boom mike gets in frame in the right corner. (00:03:00)
The System - S1-E2
Continuity mistake: Grant begins to remove the screws from the vent starting from the right side, but the top row is already missing and unscrewing 2 on a single side already makes the vent wobble significantly before the camera cuts away. (00:14:00)
The System - S1-E2
Continuity mistake: Casey is having a chit-chat with the villain/stooge of the episode, playing dumb and pretending to have a ridiculous 'system'. As she says that whenever she loses she doubles the bet "three times in a row", her hair goes from behind the shoulder to the front of the shoulder. (00:16:05)
The System - S1-E2
Continuity mistake: When Nicholas distracts Chuck the security guard with a phone call (terrible plan, since he tells him to search in a spot awfully close to the monitor he's supposed to be distracted from), he touches the papers next to the monitor and the pen in front of it, but when it cuts to him looking at the recording while Grant is working the safe, the objects are in the exact same position as before when he was looking at the money count. (00:19:55 - 00:26:15)
The System - S1-E2
Other mistake: When Nicholas impersonating Marley is going through the security cameras of the casino (none of which catching the 'double Marley' on camera exposing the trick, conveniently) there is one that follows with a cinematic motion the exact movements of the person answering the phone. They are all static cameras, just that one arbitrarily moves, without Nicholas doing anything. (00:36:50)
Plot hole: The mysterious neurosurgeon Dr. Quinn was mentioned by the fake Myles Taggart under the pretence that his presence was announced by the local newspaper. It turns out that his invitation by the university was a lie - presumably no newspaper story existed at all then, or the university would have acted on that. Taggart is exposed as a fraud, Quinn's link to him is so direct that he was even the one who invited him (instead of goading the Colonel into inviting him like it was his own idea) and yet the Colonel continues to trust Quinn blindly - he even has the whole night and day to think about this simple fact, nothing was decided on the spur of the moment.