Some of my favourite ones (not necessarily in order)
Doc to the Swedish Chef: I don't CARE if the turkey says the dog is the turkey. The dog is NOT the turkey. The TURKEY's the turkey, you turkey!
Doc: That is one worried frog.
The Count: That's one. One worried frog!
Robin: Ah, he's not the only one.
The Count: That's two! Two worried frogs! Ah-ha-ha-ha! **lightning**
Big Bird: Now then, Mr. Cook, tell me. What exactly are you going to cook for Christmas Dinner.
Swedish Chef: [Mock swedish]
Big Bird: Shredded Wheat and Cranberry sauce? My absolute favourite!
Floyd: There's Miss ham hocks when she was just a little sausage roll!
Floyd: ... and she don't look bad. For a pig!
**laugh**
Doc: I don't know how to explain it, Kermit, but I was searching through the snow, and there was Miss Piggy, with this... costume for me.
Kermit: You don't have to explain, Doc. If there's one thing Piggy knows, it's how to make an entrance.
Various people: CAREFUL ON THE ICY PATCH!!
Maureen the mink: Oh, Miss Piggy, I've seen everything you've done. I'm your biggest fan! I worship the ground you walk on!
Piggy: ... Ahaha! What a wonderful present!!
Fozzie: Hey, that's pretty good harmony for a snowman.
Snowman: Actually, I'm a snewman.
Fozzie: What's a snewman?
Snowman: Nothing, what's a-snew with you?
Ernie: Come out, Bert.
Bert: I won't.
Ernie: Come on, Bert.
Bert: Ernie, please dont make me. [Bert comes out on stage in frilly costume] Ernie, why must you always humiliate me?
Ernie: Come on, Bert. Someone has to play Mamaw, and you lost the toss.
Bert: Alright, just get it over with!!
Ernie: Cue the mouse!
Grover as mouse: I'm here, I'm here! The cute little mouse is here.
Bert: What's the bowl for?
Grover as mouse: So you can see that I am not stirring. Note how the hand never touches the spoon. Thank you! Thank you!
Piggy: Ooooh! Green fuzzy flipper slippers! Divine. Have then gift-wrapped. [laughs to camera]
((I personally quote that last one ALL the time))
Newsman: The worst blizzard in 50 years is approaching us at a great rate. The weather service reports that barometers are falling sharply. **Barometers fall from above** Oww!!
Some of my other favourite ones have already been said.