Thought of some more favorites :)
"Well, Pedro, what's on the dessert tray tonight?"
(Pedro looks through the telescope)
"I found the little girl. She is in Mexico."
(shot of faraway totally fake planet earth)
"Oh yeah, he really zeroed in on her!"
(surveillance devices working)
"This weird enough for you, folks? How's this make you feel about Santa?"
I also love their all-inclusive Christmas "carol"
and...this one is so hilarious because it's part of the actual movie, rather than the MST3K comments:
when Santa is reading the letters
(after the very funny "oh, there was a rock in that one!" and "there's a dollar in every one - my chain letter scam worked!" and "oh, man, I need a database!")
and he reads the super long letter from the child who wants things like
"a bicycle, an atomic laboratory, a machine gun..."
and Santa says the kid is telling the truth about being good, so he will bring him his atomic laboratory!! :)
"Booze helps parents care for their children." One of my fav mst3k lines.
Funniest MST3K lines for me:
When Santa is talking about the bad boys: "Oh, those little rascals!" (The MST3K audience does a fast take-off on the "Little Rascals/Our Gang" theme song).
When the devils are dancing in hell: "Oh sure, Hell got an NEA grant!"
When seeing the fumbling Merlin: "This guy trained the king of England?"
And: "That's not a doll, that's a sister!"