References to other movies
1. General W.R. Monger and the US President are resembling their Dr. Strangelove counterparts (general Turgidson and President Muffley)
2. "Extract Quantonium with extreme prejudice" - borrowed from Apocalypse Now
3. Presidential advisor running down the hall (in the scene where he undergoes many ridiculous security checks) - borrowed from The Right Stuff (the running part, at least)
5. President playing the piano for the aliens - borrowed from "Close Encounters of the Third Kind"
6. Gallaxhar is physically resembling Martians from the "Mars Attacks!" movie ("we come in peace, but we will kill you all" speech is borrowed from the same movie)
7. EXTRA: The Missing Link describing warmer climate as a "convenient truth" is obviously a reference to Al Gore's "Inconvenient Truth"
Which references did you notice?