I've never thought of Don Quixote as being a work to "make fun of" or even make light of some "crazy guy" with some mental illness.
Rather to me, it's simply a man that wanted to be something more than he was, so he went out and became that. Was he 'crazy' and 'weird'? Yeah. But was he happy? Isn't that what counts?
If I wanted to get all highschool-lit, I'd say it's a symbolic tale of finding one's own path happiness regardless of what everyone else tells you to be and do.
. . . though I could also be missing the meaning of the story, as I admittedly don't remember how it ends.
(I just finished "Chapter 5" in the version I have, but that's out of 127 chapters split over two parts. So . . . there's quite a ways to go yet.)
((Oh, and I've been reading it today even though I said there were some other books I want to finish first because I'm at work, and have my cell phone on me, but not said other books))