Hm. I never understand why people feel the need to spell out the story of a show like this in their reviews. It's a lot less funny reduced to a few hundred words.
At any rate, this wasn't a great episode in my opinion. The fishsticks joke is ok (it gets better with repetition, rather like Cartman farting in Kyle's face), and the continuity humour is funny enough, but as has been mentioned by others, it's all been done before in earlier SP episodes. It all felt a little predictable to me. Could see the ending coming from miles off, although the song was a nice touch.
That said, I don't agree with the poster who claims the show's gone downhill since season 10 - what about the utterly inspired Imaginationland trilogy? Or Night Of The Living Homeless? (both season 11) Or countless others, for that matter. I think Matt and Trey are really starting to handle their story arcs with much more confidence than they used to, and some of the episodes of the past few seasons stand head and shoulders above all other cartoon comedies around, but inevitably it's impossible to be consistently brilliant after so long - every season has filler episodes, and for me, this was one of them. Not bad, by any stretch of the imagination, but not their best.
Incidentally, City on the Edge of Forever (S02E07) - "...now that's what I call a sticky situation" - episode is a personal favourite of mine, and does indeed get a lot more out of the same continuity gag.