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: 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.