My first episode was Hiccy Burp, though I already had the general premise of the show down just by looking at the stuff they had on Cartoon Network's site some time ago and, years later, reading what others had to say about it. I didn't think I'd ever be able to watch it due to my lack of cable, but then I found this site.
Hiccy Burp wasn't the greatest episode ever IMO, but I liked it enough to try another one.
Schlock Star, the next one I watched, was what really got me into it.