Continuity mistake: When Sam and his friend drive into the park to attend the party, the colour and angle of the sun's rays seem to indicate that the sun will be setting soon. However, when Sam starts talking to Michaela's boyfriend, the sun is much higher and brighter than when Sam arrived a few minutes earlier.
Continuity mistake: When Bumblebee is caught, so are Sam and Mikaela. They were on the ground being handcuffed. But then Sam gets away and starts running for Bumblebee to stop him from being frozen. Sam is no longer handcuffed at this point.
Continuity mistake: When Sam and Mikaela are in the SUV with Simmons, the look of the backseat of the vehicle, between the two teenagers, changes when Prime appears, and provides them with his version of a sun-roof.
Continuity mistake: The rather large hole at the back of Sam's long and short-sleeved tee shirts, that appears after Barricade interrogates him and he knocks Mikaela off her moped, changes size, position etc. There are other small rips around that hole that appear, disappear and change as well.
Continuity mistake: When the troop is flying in the helicopter at the start of the movie, Epps is not wearing sunglasses. When it cuts back to him, he is, then again it cuts away and back several times and you can see an indentation on the side of his head where the Oakley sunglasses were.
Continuity mistake: In the scene where Sam and Mikaela are looking at Bumblebee's engine, both of Bumblebee's doors are open when Mikaela starts walking away. Sam jumps in the car and pleads with it to start, and the shot changes to side view from passenger side of him trying to start. Here both doors are open as well. But when the shot changes to Bumblebee starting up and Sam jumps out to close the hood, the passenger door is suddenly closed.
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: 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 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: 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.
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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