If you've played both Earthworm Jim 1 and 2, then you'll know that Tommy Tallarico used quite a lot of Classical music in his tracks for the original Earthworm Jim games. Tommy Tallarico was greatly influenced by classical composers such as Beethovan, so it's really no wonder!
What The Heck's (Evil The Cat's level in Earthworm Jim 1) musical score starts with "Night on Bald Mountain" (originally named "St. John's Night on the Bare Mountain") - by Modest Petrovich Mussorgsky (1839-1881). It then cuts into escalator music with tortured screams.
The secret level in level 5 (Who Turned out The Lights?) is "Maple Leaf Rag" by Scott Joplin, otherwise very much based on it.
The villi people (With Earthworm Jim disguised as Sally the Blind Cave Salamander in Earthworm Jim 2) was Tommy performing the first movement of The Piano Sonata No. 14 in C-sharp minor "Quasi una fantasia", Op. 27, No. 2 - Moonlight Sonata for short - by LudWig Van Beethoven (1770-1827).
Puppy Love (Earthworm Jim 2) is an arrangement of both Tarantella Napoletana (Italian Tarantella folk music) for the main part, and Funiculi Funicula as the bridge by Luigi Denza (1846-1922).
Udderly Abducted is Tango music called El Choclo by Angel Villoldo, which was premiered in 1903.
See Jim Run, Run Jim Run is the third and final movement of Moonlight Sonata.
Tommy Tallarico on the Subterranian song that plays in Iso 9000 (And Lorenzen's Soil):
"When Beethoven was asked what the motif in his 5th Symphony represented he responded "That is fate knocking on your door." The vocal in this is one of my friends saying that phrase in German."
If that's not enigmatic, I don't know what is!