Other mistake: In the scene immediately after the opening credits, Jim is talking to Melinda on the phone. Right as he's hanging up, someone calls out "Dr. Clancy? Got a minute?", to which Jim waves in acknowledgement and starts up the stairs. (Jim's spirit has been in Sam Lucas' body since season 4 and in an earlier season 5 episode, his white coat is embroidered S. James Lucas, M.D). (00:09:15)
Visible crew/equipment: When Melinda heads out to go on a run, while she and Sam/Jim are standing beside her car, in the shots facing Sam/Jim we see Jim's face, actor David Conrad, and in the car window's reflection we see Sam's face, actor Kenneth Mitchell, which is deliberate for viewers since Jim's spirit is in Sam's body. But just as Melinda says, "He worked a lot of weird hours, and liked to sleep-in a lot," it's amusing that in the reflection we can see both actors - David Conrad walking and then standing behind Kenneth Mitchell, both of whom play the same role and are wearing the same grey T-shirt.
Visible crew/equipment: After Hank Dale tells Steve Pinkus that he wants to know "How it feels to get away with murder," Hank throws a punch, and in the next wide shot we can see the second cameraman's arms holding an additional camera, presumably to film the close-up, at the right side of the screen. (00:32:35)
Visible crew/equipment: When Eli is at McShay's bar he hears the ghost beside him say, "Day after day after day," then when the bartender speaks to Eli, in the wide shots the shadow of the boom mic is visible right above the mirror. After Melinda walks in, when the bartender tells her that Eli scared all his business away, we can see in the mirror's reflection the boom mic dipping into view.
Visible crew/equipment: When Melinda is at the VFW trying to get information on Paul Evans, she and Joe are alone with his wife's ghost, and after Joe tells Melinda that she can come by anytime for scintillating conversation, it cuts to a shot facing her and we can see equipment movement at the bottom right side of the screen.
Other mistake: The captain talks about the "outflow valve", which has a distinctive rectangular shape and is fitted flush with an opening in the aircraft skin. It would be immediately recognizable by any crew member because it part of the walkaround inspection before each flight. He is holding a round pneumatic supply valve instead, which is part of the internal ductwork.
Continuity mistake: At the end of the show when Jim is making toast they show him through the window taking the toast out of the toaster and putting it on the plate. In the next shot he is walking towards the kitchen table and the plate is empty. Then while talking to his mother he picks up a piece of toast to put jelly on it.
Plot hole: Jim taking over Sam's body just doesn't make any sense. It's plausible for a spirit to temporarily take over a living body, but a dead body is dead for a reason. It can't sustain life anymore. Death isn't a temporary ailment. It's permanent. What should have happened was the same thing that happened when another ghost took over a recently deceased person, which happened in a previous episode. The dead body would decay and start to lose function. Sam's body suddenly gaining back the properties of life is completely inconsistent with what we're led to believe in the setting of the show.
Continuity mistake: After Sam reads the newspaper article about Jim's death it cuts to him dropping in to see Melinda, and when he's looking at the framed photographs on the sideboard two of the closeups of the photos are flipped shots - the positions of the frames are reversed.