If we shadows have offended,
Think but this, and all is mended:
That you have but slumbered here,
While these visions did appear;
And this weak and idle theme,
No more yielding but a dream,
Gentles, do not reprehend.
If you pardon, we will mend.

Puck speaks this towards the end of the play as a monologue to the audience, and it speaks almost the entire theme of the play which is its dreamlike state. He his explaining that if anything bad did happen then you can just forget about it because it was nothing more then a dream. Shakespeare wanted his play to seem this way, very light hearted and care-free. "And this weak and idle theme," obviously Shakespeare knew this would not be his most ground breaking play due to its nature, but he achieved what he wanted to write, something that would not offend or make his audience question, and escape from their probably troublesome lives.