Continuity mistake: Jonathan reveals the kryptonite to Clark/Dawn and Clark starts to react to it. Because of the kryptonite Clark drops the tiara he took from Chloe and it hits the floor near Chloe's hand. Then, just before Dawn is forced out of Clark's body, the tiara has slid several feet away and is now close to the furnace. Clark turns his attention to Chloe, she is faking an injury at this point, but now the tiara has moved back to be near her hand.
Revealing mistake: After everything with Dawn is over Clark goes back to the prom. Clark asks Lois if she wants to dance. Lois says "I'm not the one you want to dance with." and she nods to the door. The shot switches to show Lana walking in to the prom. When Lois makes her nod to the door Lana would have been completely out of sight. Lois nods before Lana even enters the room.
Suggested correction: We never see Lana walking into the gym. She's just standing at the door, nervous about going in. We don't know how long she was standing there. Not to mention the fact that the scene of Lana at the door could have happened at the time Lois was making her comment and Lana walked in before the first time we see Lois look at the door, before she nods.
Continuity mistake: Jason accesses Lex's computer and Lex catches him. After a discussion on an email Jason found Lex says "Burying ladies in the backyard isn't exactly a hobby of mine, Jason." Lex then just stands there staring at Jason. During their stare down the camera jumps back behind Lex and then back to behind Jason. During these camera changes the lighting on the left side of Lex's face changes. When the camera is behind Jason, Lex's left side is dark. When the cameras is behind Lex, Lex's left side is lit up.
Continuity mistake: Lana looks over the edge of the crater and there is a fire right in front of her on the inside rim of the crater. When the shot changes and pans up to an overhead view of the crater and ship that fire is missing.
Continuity mistake: Clark had been wearing his cap and gown for a while. When he takes them off while coming off stage the blue shirt he has on underneath has fresh raindrops on it like he had only put the cap and gown on a few minutes before the shot.
Continuity mistake: The raindrops on Clark's shirt disappear and reappear between shots. Clark's shirt is dry when he turns to Chloe and asks "I'm not normal?" but before and after this his shirt has raindrops on it. This happens again a few moments later as Lois starts to talk about "panicking in times of crisis", Clark turns towards Lois and his shirt is dry.
Revealing mistake: As the helicopter that Lana is in dodges the falling meteors in mid-air, the camera shot focuses in on the cockpit. If you watch Lana's position as she first starts to appear she is semi-transparent and the frame of the window behind her is visible through her body.
Continuity mistake: Jason Teague arrives at the Kent farm. He fires a shot into the windshield of the Kent's truck. So we obviously know the gun is loaded. Later, inside the Kent's house, Jason still has Jonathan and Martha held hostage. After Jason mentions the symbols burned into the field Martha says she doesn't know what he is talking about. Jason gets upset and racks the shotgun but when he does no shotgun shell, used or unused, is ejected. Now Jason would have had to keep the gun loaded while moving Jonathan and Martha back to the house as he would have had no time to unload and reload his gun.
Other mistake: In the opening credits of the original broadcast, Kristin Kreuk's first name is misspelled as "Kristen." The credits sequence, which was new for Season 5, was corrected by the time the second episode of the season aired.
Continuity mistake: The blood on Lana's face is different then how it was in the previous episode. While at the crater in Commencement she has two distinct lines of blood on her face. One on her left cheek is thick and the one on the right cheek goes down past her lips. While at the crater in this episode the left line is then while the right line is shorter. These two scenes should be identical since Arrival picks up right after Commencement.
Plot hole: Chloe has to use Lex's thumbprint to access the safe inside level 3. She gets his fingerprints by lifting it off of the flashlight he picked up for her earlier in the caves. The problem is when Lex picked up the flashlight and gave it to Chloe he had only touched the back half of the flashlight, but when Chloe lifts Lex's print she gets it from the opposite end. Since Lex did not touch that end there should be no fingerprints for her to lift and use on the security door.
Continuity mistake: When Clark's parent show up at the house Clark hurries up and acts busy. He grabs 4 boards and moves them from one part of the kitchen to the other and leans them up against the wall. When Clark turns around to face his parents there are only 2 boards leaning on the wall.
Continuity mistake: When Gabriel shows up to help Chloe the shadow of his bike shows it to be about noon. According to the show it should only be between 6:30 to 7:30am.
Continuity mistake: When Lois and Arthur are sitting at the end of the dock, (before Arthur begins to hear the piercing ringing sound) the position of the bikini lace hanging down Lois' back keeps changing between shots.
Continuity mistake: The water level in the glass that Lex taunts Aquaman with changes levels throughout the scene.
Continuity mistake: When Clark first enters the club, the stripper on stage is taking her top off, then in the next shots of her, she still has her top on.
Revealing mistake: After Lana is warned by Chloe that Clark has gone all 'Captain Paranoid', she examines the silver 'meteor rock' more closely. We see a shot of her hand holding the 'meteor rock' but the hand that is shown is obviously not Kristin Kreuk's hand.
Continuity mistake: When Clark's truck stops rolling over the hood is stuck open. As Clark pops up from the front seat the hood is down for the camera to get a shot of Clark.
Continuity mistake: Clark is poisoned by a silver kryptonite splinter. When Clark is stabbed, the splinter is in his left index finger. Then, in the scene with Fine after class, (less than twenty minutes later,) Clark is seen rubbing his right index finger.
