I always find it amusing whenever I'm watching a movie and suddenly I hear music similar to classical pieces but not quite them. Thought I'd start a list of plagerisms I've heard over the years, and would be happy for any contributions.
Mozart: Ave Verum Corpus. Found in the Lion King.
Beethoven: Piano Concerto No. 3, 1st movt. Found in The Dark Knight.
Beethoven: Symphony #5, 2nd movt. Found in Restoration.
Beethoven: Piano Concerto #5, 1st movt. Found in My Best Friends Wedding
Schumann: Symphony #3, 1st movt. Found in Willow.
Dvorak: Symphony #9, 4th movt. Found in Jaws
Tchaikovsky: Symphony #4, 2nd movt. Found in Willow.
Mussorgsky: Pictures at an Exhibition. Found in Star Wars, Empire Strikes Back.
Holst: The Planets, Mars. Found in Gladiator (most blatantly, and a lot elsewhere- just the rhythmic pattern).
Sibelius: Finlandia. Found in Air Force One.
Sibelius: Symphony #3, 1st Movt. Found in Lord of the Rings.
Prokofiev: Ivan the Terrible. Found in Glory
Prokofiev: Violin Concerto #2, 1st Movt. Found in A Beautiful Mind.
Vaughan Williams: Tallis Fantasia. Found in Glory.
Ok wow... didn't expect to think of so many. If you'd like links, I'd be happy to provide them, but not going to take the effort before I know if someone is interested or not.