Firestarter - S4-E1
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.
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.
Suggested correction: This is a fictional show that pushed the boundaries and constantly changed the rules; how is this a mistake?
I tell myself that Sam's injuries were not as extensive as prom ghost so his body was able to stay alive.
I think what happened is that Sam jumped out and went into the light before they were able to revive him. Had he waited just a few more seconds next to his body He would have gone right back in. Some people die for a few seconds, and then they're able to bring them back through CPR or using the paddles and shocking his heart, etc.
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.
Heart & Soul - S4-E8
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.
Visible crew/equipment: After Sam/Jim tells Melinda that he'll be leaving and doesn't know how long he'll be gone, as he drives away the reflection of the large reflector screen can be seen on the pickup's vent window.
Continuity mistake: While Melinda's trapped underground with the rising water flooding the utility vault, when Eli and Jim go down below Eli takes off his shoes and jacket, the camera pans up from the churning water and we briefly see Eli's bare feet. The next shot we see him taking the socks off.
Imaginary Friends and Enemies - S4-E6
Continuity mistake: In the scene in the woods where we first see Owen's ghost, as the camera cuts back and forth between Melinda talking to Owen and what her friend sees, the two women are alternately closer and then significantly farther apart. They're supposed to be standing basically in the same spots, only taking maybe one or two small steps during Melinda's conversation with Owen.
Continuity mistake: When Eli tries to use a card to open Zoe's door, the card breaks. He is holding on to the larger piece of the card in his right hand when this happens and the smaller piece is in the frame. He gets the other piece and the shot changes to him suddenly holding the smaller piece in his left hand, as well as the card having been flipped around (the strip is seen in both shots, and the two shots face in opposite directions).