Deliberate mistake: At the corner of the roof, Sam clutches the statue as he protects the All Spark from Megatron, who then destroys the statue causing Sam to fall. In the overhead shot of Sam falling, as the chopper flies by, we see the All Spark leave Sam's grip and actually fall behind him. Yet, in the next close-up the All Spark is safely held in Sam's arm again. (02:06:50)
Continuity mistake: At Bobbie B's, when Sam first opens Bumblebee's driver-side door, the gas pump's white steel guardrail is directly behind him, aligned with the driver's seat, but when all the windows shatter, Bumblebee's front fender is aligned with the guardrail, though Bumblebee has not moved. Same goes for the VW Beetle beside the Autobot. (00:14:00 - 00:15:10)
Continuity mistake: When Ron and Sam, followed by Bumblebee, make the U-turn in front of Bobby B's and then park, the spinning 'Bobby B. sez...let's talk deals' sign is to the left of the three vintage gas pumps, near the clown. When Bobby B. puts his arm around Sam's shoulder and says, "Sam, your first enchilada of freedom..." the spinning sign is now on the other side of the pumps, where there wasn't a spinning sign previously. (00:12:10 - 00:13:15)
Continuity mistake: When Ron and Sam park in front of Bobby B's, there are three cars parked in front of the three pumps - a white vinyl top, a wagon, and a red car. When Sam says, "You said half a car, not half a piece of crap, Dad," the red car has been replaced with an old blue Plymouth, specifically for the "50-year-old virgin" joke, because the red car is back in following shots. (00:12:20)
Continuity mistake: Before Barricade interrogates Sam, the Decepticon throws Sam on the windshield of a car, and a wheel falls off the car's roof, but then reappears back on the roof in a following shot.
Continuity mistake: After Mikaela hacks away at Frenzy, when Sam kicks him like a football he uses his right foot in the close-up, but his left foot in the wideshot. (00:54:40)
Continuity mistake: When Barricade interrogates Sam about the glasses, the cracks on the shattered glass windshield under Sam disappear, reappear and change characteristics between the interior (inside the car), overhead and close-up shots. (00:50:35)
Continuity mistake: After Sam is knocked off the pink bike, he ends up on the ground as Barricade, aka the police cruiser, drives forward causing Sam to keep backing up, which leaves the bike near the back of the cruiser. Yet, when Barricade threatens Sam with its weapons, the bike is right beside the cruiser's front end again. (00:49:35)
Continuity mistake: In the scene where Sam is being interrogated at the police station, the cop catches the drug bottle with the bottom facing up. When it cuts, the top is facing up. (00:38:20)
Continuity mistake: Aboard Air Force One, when Frenzy kills the first two Secret Service agents, the second agent falls back into the hallway, but his feet are still in the room over the bottom raised lip of the doorway. When the third agent fires on Frenzy, the legs of that second agent are lying flat on the room's floor, right beside the first agent that was hit. Note that the agent's legs are also beside the shelving unit, which is a good distance from the door. (00:31:45)
Continuity mistake: When Mikaela looks under the hood and fiddles with Bumblebee's distributor cap, her long hair is either behind her shoulders or in front, depending on the angle of the shot. (00:25:15)
Continuity mistake: The number of the surviving ranger team changes, as Keller announces the base attack a shot is showed of 8 rangers and Mahfouz (the young boy), then as the team is attacked by Scorponok one team member is killed, but seconds later as the team runs down a dune they are still 8 rangers. One runs past the camera quickly while 7 and Mahfouz comes down the dune, later as Epps directs the air support he claims they are only 7 rangers, and as the Huey lands there are only 7 rangers.
Continuity mistake: When Sam is on the roof, the streets below appear normal, but when Megatron hits the building and Sam falls, there is destruction on the streets.
Other mistake: When Optimus Prime comes powersliding into Mission City, take a close look at the ground. You can see skidmarks from previous attempts. (02:00:00)
Revealing mistake: When Optimus Prime is powersliding into the city, right before he transforms, you can see that the truck is actually a CGI replica, because the blue is much lighter than it was a second ago, when he already burst out of the shadow of the alley.
Visible crew/equipment: When Sam is talking to Barricade, in the shot taken inside the car, a camera is reflected by the windshield. (00:49:55)
Continuity mistake: When Epps and Lennox spot Starscream thinking he's Air Force, Epps is holding the mic up to his mouth with his right hand and says, "Raptor, Raptor, do you copy?" Next shot, however, the mic is being held up in his left hand.
Continuity mistake: At Hoover Dam, when Sam tells Banacheck the terms of his cooperation (which include expunging Mikaela's juvenile record), Mikaela's high-gloss lip gloss disappears in her close-up, then reappears. (01:36:00)
Continuity mistake: As we are hearing Prime explaining, "They're a young species, they have much to learn," we see S-Seven's SUVs pull up to the curb at Hoover Dam and the doors open, right beside the vertical guardrail posts with the horizontal beams. In the next close-up, all of the horizontal beams have vanished. (01:34:25)
Continuity mistake: When Sam pursues Bumblebee on his bike, as he is on the phone with 911 there is a close-up of Sam's feet pedaling. After Bumblebee breaks through the gate, there is another close-up of Sam's feet pedaling, but now the gears/chain are different. (00:33:50)
Answer: Because the Decepticons didn't know where Megatron ended up for the last 100 years. Bumblebee arrived on Earth as a scout to check out for any clues, found the glasses on Ebay, signalled the other Autobots, which prompted Blackout and Frenzy to investigate the base in Qatar, which lead to Blackout downloading the base computers and Frenzy hacking the computers aboard the aircraft later leading to the discovery of Megatron's whereabouts.
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