The first act had the best lines, in my opinion. Feel free to clarify any I misquote since I'm paraphrasing from memory, and list any quotes you love!
"Aww.. Nibbles is leaving her with five hamster babies." Lisa: "She already ate three of them." Marge: "Seems sensible to me."
Milhouse: "My eyebrows! My beautiful eyebrows!" Bart (wearing eyebrows as muttonchops): "Here the are, gov'nor."
Homer: "Unblowupability is a word that has been tossed around.." (rocket#2 explodes)
Homer: "I would just like to say a few words before launch. Will all Nerds please leave the launch area." All the nerds and Milhouse walk away grumbling
Bart: "The rocket is veering off course. It's out of control!" Homer: "I have prepared for this. Nibbles, to your left, you'll see a green handle. Pull it for a three second controlled burn." Nibbles looks at the lever, then to his right at a big eject button. Whacks the button with his head.
Milhouse admiring Flanderses' rocket: "Look at that yaw control!"
50s SciFi captain: "Oh no! Space Air is flooding the ship! Put on your goggles to breathe!"