When I hear the Queen of the Night’s “revenge” aria from Mozart’s The Magic Flute I think of car commercials. Although I could not remember which car. (Looking it up, I find that it was in Volvo ads.)
You can’t listen to Bach’s “Air on the G string” without thinking about “skipping the light fandango” or worse…
And, for me, 30+ years of United TV ads, as well.
Bach’s “Toccata and Fugue in D Minor” is the villain’s theme song in many horror movies.
I really disliked that movie (the factual inaccuracies drove me up the wall) and I figured the soundtrack would just be Queen’s zillionth best-of collection…but that’s actually a really cool touch.
Whereas Delibes’ “Flower Duet” is mainly known as the British Airways Song.
For me, Carmen’s “March of the Toreadors” is 50% associated with the Gilligan’s Island version of the “Neither a borrower nor a lender be” speech from Hamlet, 50% associated with Palm Dairy Products:
here, Metallica’s version, been using “Ecstasy of Gold” in their concerts the past 15 or so years, they do right by this wicked song.

For me, Carmen’s “March of the Toreadors” is 50% associated with the Gilligan’s Island version of the “Neither a borrower nor a lender be” speech from Hamlet,
Yup, that’s the association for me with that song.
And, speaking of that episode, the Habanera aria from Carmen is 50% Gilligan’s Hamlet soliloquy (“I ask to be, or not to be”), and 50% the singing orange from Sesame Street.

The standard for this used to be associating Rissini’s William Tell Overture with The Lone Ranger, but I suspect that modern kids no longer suffer from that affliction – who the hell watches those old Lone Ranger shows anymore?
For those of us who grew up on Saturday matinee westerns, it will always be associated with the masked man.
“As Time Goes By” is always associated with “Casablanca” for many.
It’s long been a general rule of mine that if a company uses a popular song or classical theme I like in its ads, I will mute the ads and avoid buying its products.
When I grew up, they were still showing Lone Ranger repeats, but I’ve long since associated the William Tell Overture with, well, just the overture.

Whenever she hears Wagner’s Ride of the Valkyrie my wife inevitably thinks of Emer Fudd singing “Kill the Wabbit! Kill the Wabbit!”
(Although a big Bgs Bunny fan, I think of Apocalypse Now.
In neither case, was the original “ruined” IMHO. perhaps another term? I mean I get where you are coming from- some great old classical music might be forever associated with a cartoon .

Elmer Bernstein’s theme for The Magnificent Seven – Marlborough cigarettes.
Not any more, the movies have outlasted the product ads.

Gounod’s Funeral March of a Marionette – "Alfred Hitchcock Presents
Oka, that one is pretty solid, I cant think of that tune with old Alfred there.

Ponchielli’s “Dance of the Hours” from La Gioconda – Allan Sherman’s “Hello Muddah, Hello Faddah (A Letter from Camp”) I heard this LONG before I heard the opera. In fact, if Allan Sherman hadn’t ruined it for me, Disney’s Fantasia would have.
I think Fantasia did the opposite of “ruin” classical music. They popularized much great music.

In my mind, “Stuck in the Middle with You” will always, indelibly, be the music of a sadistic psycho guy cutting off another guy’s ear (Reservoir Dogs).
I didnt care for the film, so that one- nope.

Whenever I hear Don’t Fear the Reaper I automatically think of “Needs more cowbell!”.
Fortunately, SNL is not as powerful as you think.
They did a great ad with Pizza rolls, with William Tell Overture, with the Lark commercial guy objecting, then the Lone Ranger step out and tells the coffin nal spokesperson what for. Of course, there also could have been a Swiss with a Crossbow…

Bach’s “Toccata and Fugue in D Minor” is the villain’s theme song in many horror movies.
I associate it with 20000 Leagues under the Sea and Fantasia.

Whenever she hears Wagner’s Ride of the Valkyrie my wife inevitably thinks of Emer Fudd singing “Kill the Wabbit! Kill the Wabbit!”
“You know, it is so sad. All your knowledge of high culture comes from Bugs Bunny cartoons.” (Elaine Benes, Seinfeld)
Last night they played Glory Glory Hallelujah and thought of another version from childhood. Then I found out that I only knew the first line and realized how bad the rest of it was - especially now.
And On Top of Old Smoky is On Top of Spaghetti in my mind.

Fortunately, SNL is not as powerful as you think
Yes, but younger people have taken it as a go to slam on older artist groups. Without ever having actually listen to the song. That is what irks me. I get past it.

Me, science fiction fan that I am, invariably think of 2001: A Space Odyssey
As do most people when they hear “Sunrise” from Strauss’s Also sprach Zarathustra.

Ponchielli’s “Dance of the Hours” from La Gioconda – Allan Sherman’s “Hello Muddah, Hello Faddah (A Letter from Camp”) I heard this LONG before I heard the opera. In fact, if Allan Sherman hadn’t ruined it for me, Disney’s Fantasia would have.
This was perfomed at our local symphony’s concert this spring. When the orchestra got to the appropriate part, there was an involuntary giggle that spread through the audience. I was sure everyone there had Allan Sherman on the brain right then and there.

Bach’s “Toccata and Fugue in D Minor” is the villain’s theme song in many horror movies.
Also the TV commercial for Circuit City’s “Midnight Madness” sales.
While I wouldn’t say the song was “ruined,” if you grew up in New England during the 1970s, hearing “Nutty” by the Ventures only meant one thing:
I can’t listen to Ludwig Van without getting physically sick…