magnificent.masterpiece. i can't even describe it. Although there is a simple routine that they use.
1) the couch gag(although it's not always different.I have watched most of the episodes and there was repetition, but it's hard to make 662 different couch gags.)
2) they start the episode with something really unrelated to the main story but they link it with the main point which is really hard and you need a lot of creativity to think of a main story then create little stories and make a connection between them and that is why i'm speechless and love this show.
3) remember one thing whatever happens in that episode, stays in that episode and there is no whatsoever connection between episodes.(but they sometimes joked about it but it had no connection to the main story)