Directed by: Conrad Vernon, Rob Letterman
Starring: Kiefer Sutherland, Reese Witherspoon, Seth Rogen, Hugh Laurie, Will Arnett
Question: What song was the President playing on the synthesizer?
Answer: Axel F by Harold Faltermeyer, which was originally used in the movie Beverly Hills Cop.
Question: If Derek values his career to Susan, then why did he ask her to marry him in the first place?
Answer: Image. A good-looking man. A beautiful woman at his side. It would look good in the news.
Factual error: Gallaxhar scans the galaxy to find the missing quantonium. The scanner zooms in on earth, showing it to be very close to the center of the galaxy. Earth is actually nowhere near the center of the galaxy; it's located much closer to the outer edge.
The President of the United States: Somebody think of something, and think of it fast!
Chosen answer: Well, it's a fiction movie; some suspension of disbelief is always needed. There could be a number of explanations: for instance, lifeforms such as insects on the grass, bacteria inside them or even grass itself, being unable to absorb quantonium. It might affect only sentient beings. Or Susan might even be the first being to get in contact with the substance - this would be possible depending on the shape of the meteorite container, the exact means by which quantonium touches her body - which isn't shown... but, first and foremost, this happens because its not happening would leave the filmmakers with a plot issue to be dealt with - so, other beings don't grow simply because they don't.