Yes, this episode is primarily made from clips of previous episodes. At the very end, the writers break the fourth wall and admit how cruddy it is when a "long running series does a cheesy clip show." They acknowledge that it's kind of a shady thing and in my opinion, that's what makes it funny. Also, making fun of Paint your Wagon was pretty excellent. I'm a fan of any episode that features at least one song. This episode is nothing but songs so it wins from that perspective too. Is it the best Simpsons episode ever? Not really, but it really was a great attempt at poking fun at the series especially in a time where the series wasn't as sure of it's continued success. Overall I give this episode a solid 7/10.