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.
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)
Continuity mistake: When Bobby B. walks with Ron and Sam to the main used lot, where Bumblebee and the VW Beetle are located, most of the cars opposite Bumblebee and to its side actually change make, color, etc., from the time Ron makes the U-turn, to when all the windows shatter and shots between. Examples are: there is a camper parked in the fifth space which changes to a car; the yellow hatchback behind Sam when he opens the car door changes to a light blue car; and the two blue cars (one with a spoiler) parked beside Jaime, the ostrich, which change to a dark car and yellow hatchback. (00:12:10 - 00:15:10)
Continuity mistake: When Ron (holding a flashlight and lantern) is looking through Sam's bathroom window, saying, "Judy, better call the city. We got a blown transformer...," there is no windowbox under that window, which was there earlier. Yet when Prime says "Ironhide, you know we don't harm humans! What is with you?" the rather large windowbox full of flowers is back up under that bathroom window. (01:15:50)
Continuity mistake: When one of the Autobots knocks out the power transformer at the Witwicky house the lights all go out, however in following shots the lights in the house have all come back on again.
Continuity mistake: After Ratchet says: "The boy's pheromone levels suggest he wants to mate with the female", Mikaela scratches her head, but in the shot directly afterwards, her hand is instantly down. There is nowhere near enough time for her to put her hand down again. (01:03:50)
Continuity mistake: When Bumblebee's legs are destroyed, as Sam leans over in front of him and asks if he's alright, Sam wears blue patterned boxers, but when Lennox runs up to Sam, who is standing on the tow truck helping Mikaela hoist Bumblebee, Sam's boxers are grey (as seen between his white tee and jeans). Then, when Sam is on the roof running, after the chopper is hit, his boxers are blue patterned. (01:53:45 - 01:57:10)
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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