Continuity mistake: In the scene where Gru first meets Lucy Wilde, Gru takes out his freeze ray and fires it at Lucy. Lucy stops the freeze with a flame gun thing and then she walks over to him and tazes him. Gru then drops the freeze ray, but it disappears when she goes to put Gru in the boot of her car.
Plot hole: Lucy jumps from the airliner and flies her hang-glider straight to Eduardo/El Macho's Cinco de Mayo party to find Gru. How did she know Gru would be there? He had no intention of going and only did so after he was pestered into it by the girls on the very night of the party, so he couldn't have told her himself. Shouldn't she have gone to his house instead?
Continuity mistake: After watching El macho activate the dance floor key to the lift, Gru then does the same thing. During the first attempt, Gru spills guacamole on the floor, his nacho hat gets sliced in half and more guacamole falls. He then throws the nacho hat to one side and tries again. But in the shot from above the guacamole on the floor has vanished.
Continuity mistake: When Tom the Minion dressed as a maid is hoovering, he answers the front door by opening it towards him as does the minion who looks out of the door after Tom has been taken. In the scene with Gru sat on the steps in the rain, sad that Lucy is off to Australia, Agnes comes out with an umbrella, but now the door opens outwards.
Plot hole: The rocket is launched with Gru and Lucy attached to it. All of the minions are around them at El Macho's lair at this point. Considering a rocket travels at several hundred miles per hour, when they jump off it almost a minute later they should be several miles away at the very least, but three Minions appear on a boat shortly after. There is no way the three Minions could have reached Gru and Lucy all the way from the lair in that short time.
Continuity mistake: When Gru is attempting to unlock the floor key pad, he triggers an incorrect key and some fire is blown at him. Some smoke is left all over his face. Gru triggers another incorrect key and some darts are launched at him. The smoke is still there, but as he falls over, most of the smoke on his face has gone. The smoke on his right cheek is still there, but has still vanished from his face.
Continuity mistake: When Gru follows Eduardo through the corridors, he stumbles to find him dancing along a floor key pad to unlock the lift. It is also shown that if a key is pushed incorrectly, the key turns red and a weapon is launched at the person on the key pad. When he begins to activate the key pad, the first key he steps on is the key second to the left on the first row and continues the rest of the pattern. Gru then attempts to do the exact same sequence. The first key he steps on is the key second to the left on the second row, despite the fact that Eduardo actually triggered the first sound effect with the key on the first row, second to the left. Despite this, the sound effect is still correctly triggered.
Audio problem: As Gru attempts the dance floor key, some of the guacamole from his nacho hat falls out of the hat and lands on one of the keys which then triggers one of the sound effects. An axe then chops off the rear end of his nacho hat and lands on the part of the dance floor behind him, but no sound effect is made from the floor.
Factual error: In the opening scene all metallic objects are dragged upwards to the magnets on El Macho's aircraft, including the coins used by the Russian guards in their card game. No country on earth makes coins that are magnetic or capable of being magnetized - it's an important security consideration.
Continuity mistake: When Doctor Nefario is having a send off, he begins to blast off in his scooter very slowly. The shot after he says "This may take a while", the Minions begin to leave the area, yet in the next shot, the other Minions have vanished completely. There was nowhere near any time for them to have left the area that quickly.
Continuity mistake: When Gru is making balloons with his balloon gun thing he attaches an inflated unicorn balloon to the door frame and an exterior shot of the front lawn is shown. This shot shows a playhouse on the right hand side of the lawn. Later on, when Lucy arrives at the house, the playhouse is no longer on the lawn.