What is interesting or puzzling about Act 5 of A Midsummer Night's Dream by William Shakespeare?

Perhaps the most interesting and puzzling part about Act V is the epilogue, where Puck tells the audience that if the play offended, to think of it as merely a dream. We might wonder why we should treat a play, which we know is a piece of fiction anyway, as a dream? Does Shakespeare want us, as sometimes happens on television shows, really to think of everything that happened as merely a dream? What we have seen may seem fantastic and magical, but it follows a certain logic, especially with the use of love potions, that does not seem dreamlike. Puck leaves it up to us, however, saying:

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 . . .

Much of Act V is dominated by Pyramus and Thisbe, the play Bottom, Quince, and the other working class people stage to celebrate the weddings. At this point, the comedy falls to an almost slapstick level as the actors forget their lines and mix up their words, inviting audience laughter and commentary. For instance, Bottom playing Thisbe, mixes up sight and hearing, saying:

I see a voice . . . I can hear my Thisbe’s face . . .

It is interesting and perplexing that Shakespeare chooses to end with a play within a play that makes ridiculous some of the serious themes about love he brings up in the first four acts.