I am not one of those people who complains about "themes" in kids shows and I often get angry at people who see themes where there are none and while I'll admit my kids love this show and I laugh with them the 'elves are there to serve the fairies is quite a strange theme. I know the fairies are often portrayed as a bit helpless without their wands and the king in particular is a buffoon but the elves seem to be tugging their forelocks and are only too happy to inconvenience themselves for their fairy masters.
As I say it is funny, the kids will love it, you'll probably laugh too but that theme spoils it for me just a tad.