Gonzo14 said:
I didn't know they changed it between seasons (well I knew they changed it after season 1, but I thought that was it)
Here are the differences between the openings after season two:
Season 3: the shot of Zoot and Rowlf is different, after the cast says "it's time to get things started!", the audience says, "why don't you get things started?", and different music plays when statler and waldorf appear (and in some episodes from the third and foruth seasons, statler and waldorfs spot is replaced by a brief backstage or orchestra scene).
Season 4: the opening is shorter. After the monsters appear, we see two rows of arches appearing at the same time and the males and females appear at once, singing, "it's time to play the music. it's time to light the lights! it's time to get things started!", and then the audience says their line and it continues from how the third season closing ended.
Season 5: this one is longer (i am not sure whether this opening is longer than the first season opening). The shot of Rowlf and Zoot changes again, the shots of women and men are both changed (but they both appear seperately again), the line from the men once again ends with "it's time to raise the curtains on the muppet show tonigth" (which was used in the original opening). Then Statler and Waldorf sing a verse of the show (so their spot in the opening is the same for every last season episode), then Animal plays a brief drum solo, then Lips and the trombone lady play their instruments (a trumpet and a trombone), then we see two (or possibly three, I can't remember) stacks of arches with muppets saying "but now let's get things started", the audinece sings "why don't you get things started", and then it ends the way it did in the last four seasons (starting with kermit singing a verse and the screen widening to reveal all of the characters in arches).
I hope this helps.