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.
Revealing mistake: When Ironhide shouts, "Incoming!" as Starscream fires on them, Lennox and Epps are blown backwards and slam onto the ground. The shot of them hitting the ground and the next close-up of Lennox are flipped shots. Note the reversed 'Broadway Bar' sign and Lennox's watch. (01:53:45)Super Grover
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)Super Grover
Other mistake: When checking the eBay auction for his ancestor's glasses, the seller name is listed as 'Ron Witwicky'. eBay would list Sam's user name - 'ladiesman217' - as the seller, not a full name that isn't even his. It is clearly established throughout the film as the glasses are being sold through Sam's own account. (00:17:40)