"M*A*S*H" (TV series) --The scene with Zoidberg, iHawk, and the jellyfish alien is a parody of M*A*S*H, right down to the music at the beginning and the alternately maudlin/irreverent tone. --iHawk a parody of Hawkeye Pierce (Alan Alda), and the jellyfish nurse is Hot Lips Houlihan
"Dizzy" by Tommy Roe (1969 song) --Nixon sings it in the shower
"Walking on Sunshine" by Katrina and the Waves (1983 song) --Fry sings it while scrubbing Kif
"Starship Troopers" by Robert Heinlein (novel) --The humans being the alien invaders, defeating the strange indigenous creatures in war --Uniforms similar to the 1998 film
Also, several Star Wars references which I'll leave to other people.
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