Continuity: In the wedding, Elliot hands over a drink to Amanda. She accidentally blows off the yellow mini-umbrella of her drink. Elliot licks the stick of his pink mini-umbrella and puts it in Amanda's drink. The next scene shows Amanda still has the yellow mini-umbrella on her drink, and Elliot still has his pink mini-umbrella on his drink. Although, in a film about how perception effects reality...maybe the umbrella was blue!
Factual errors: Depiction of quantum mechanics in the movie bears no resemblance to the real theory of that name. In particular, the common misconception that the "observer effect" is dependent upon a sapient, human observer is incorrect. If any object interacts with any other, and either requires information regarding the current state and properties of the other, then that constitutes an observation.