"What’s the difference between a bowl of moldy…

“Bad salad” and “sad ballad” is a spoonerism. “GAYLORD CARTER, in his Grin, Sing and Bear It (if you can) Club, at Don Lee’s yesterday morning, after a beautiful selection, intended to say, ‘That was a SAD ballad’—instead he said, ‘That was a BAD SALAD!’” was printed in the Daily News (Los Angeles, CA) on December 16, 1936. “Bad Salad: Sad Ballad” was posted on Reddit—Spoonerisms on November 10, 2014.

The spoonerism is often made into a riddle. “Q. What’s the difference between a mouldy lettuce and a dismal song? A. One’s a bad salad and the other’s a sad ballad” was printed in The Sun-Herald (Sydney, New South Wales) on December 5, 1976. “What’s the difference between rotten lettuce and a depressing song? Rotten lettuce makes a. bad salad while a depressing song is a sad ballad. (By Richard Lederer)” was posted on the newsgroup alt.callahans on June 17, 2000. “The difference between a moldy vegetable and a depressing song? One is a bad salad, the other is a sad ballad” was posted on Twitter by Tony Blackburn on March 21, 2011. “What’s the difference between a bowl of moldy lettuce and a depressing song? One is a bad salad, and the other is a sad ballad” was posted on Reddit—Cleanjokes on June 14, 2021.

Newspapers.com
16 December 1976, Daily News (Los Angeles, CA), “Slim’s Pickin’s” by Slim Barnard, pg. 14, col. 6:
GAYLORD CARTER, in his Grin, Sing and Bear It (if you can) Club, at Don Lee’s yesterday morning, after a beautiful selection, intended to say, “That was a SAD ballad”—instead he said, “That was a BAD SALAD!” That gag ought to be worth 25 bucks to Gracie Allen. And 10 cents to Gaylord Carter.

Newspapers.com
5 December 1976, The Sun-Herald (Sydney, New South Wales), pg. 83, col. 3:
RIDDLES
Q. What’s the difference between a mouldy lettuce and a dismal song?
A. One’s a bad salad and the other’s a sad ballad.
—Renu Singh (10),
Torrens, ACT.

Newspapers.com
8 October 1978, The Sun-Herald (Sydney, New South Wales), pg. 111, col. 6:
Q. What’s the difference between a mouldy lettuce and a dismal song?
A. One’s a bad salad and the other’s a sad ballad.
—Vicky Strachan (12),
Geelong, Vic.

Newspapers.com
4 July 1982, The Sun-Herald (Sydney, New South Wales), pg. 93, col. 7:
Q. What is the difference between a mouldy lettuce and a dismal song?
A. One is a bad salad, and the other is a sad ballad.
—Lisa (12), Casino St. South Lismore.

Google Groups: alt.chips.salt-n-vinegar
s-n-v shortage
Bams Horses
May 23, 2000, 3:00:00 AM
(...)
I do like lettuce in a salad. But always remember to wash your lettuce, to avoid lettuce lice. Vinegar usually washes most of these lice away. A mouldy lettuce is very dismal and will make a bad salad, which you could sing about, in a sad ballad, “Only Lettuce Bleed”.

Google Groups: alt.callahans
“Puns of the Weak” 6-16-00
Stan Kegel
Jun 17, 2000, 3:00:00 AM
(...)
What’s the difference between rotten lettuce and a depressing song? Rotten lettuce makes a bad salad while a depressing song is a sad ballad. (By Richard Lederer)

1 January 2001, New Straits Times (Kuala Lumpur, Malaysia), “How a punster tells bedtime stories” by Oh Teik Theam, The City Advertiser, 2* Edition, pg. 5:
The Grasshopper wasn’t such a bad insect after all. After dinner, he entertained his benefactors with his conversation, interspersed with jokes from his personal repertoire. And remembering what he ate a few minutes ago, he said, “Rotten lettuce makes a bad salad. A depressing song is a sad ballad.”

Twitter
Nick Nash
@Bright_Sorcerer
The difference between a moldy vegetable and a depressing song? One is a bad salad, the other is a sad ballad.
11:11 PM · Jun 2, 2009·Twitter Web Client

Twitter
centrozoon
@centrozoon
The Sad Ballad of (the Bad Salad of) Tori & Kirk. http://bit.ly/dofDSi
5:45 PM · Apr 13, 2010·Facebook

Twitter
Tony Blackburn
@tonyblackburn
What’s the difference between a limp lettuce and a miserable song ?...One’s a bad salad,the others a sad ballad.
1:03 PM · Mar 21, 2011·TweetDeck

Twitter
Listen & Learn
@ListenandLearn1
Spoonerisms: #words or phrases in which letters or syllables get swapped.
Bad salad (Sad ballad)
Soap in your hole (Hope in your soul)
4:07 PM · Dec 9, 2013·TweetDeck

Twitter
homeopathical
@homeopathical
Spoonerism of the day: ‘sad ballad’ -> ‘bad salad’ 😊
5:29 AM · Feb 27, 2014·Twitter for iPhone

Reddit—Spoonerisms
Posted by u/LapsedPacifist November 10, 2014
Bad Salad: Sad Ballad.

Twitter
Witless Protection Program
@LindaWrite
The Sad Ballad of the Bad Salad
My lettuce was wilted
Tomatoes were rotten
The dressing? Abhorrent
Veggies fuzzy like cotton
Quote Tweet
RubberBanned
@R0brBun7
· Aug 9, 2017
Replying to @LindaWrite
The other day I ate a bad sallad
9:24 PM · Aug 9, 2017·Twitter for iPhone

Twitter
North by Northwest
@nxnwcbc
Spoonerism: A ‘bad salad’ becomes a ‘sad ballad’. Word Guy Jonathan Berkowitz takes us through the best spoonerist puns. ON NOW
10:11 AM · Oct 1, 2017·TweetDeck

Reddit—Cleanjokes
Posted by u/chacham2 June 14, 2021
What’s the difference between a bowl of moldy lettuce and a depressing song?
One is a bad salad, and the other is a sad ballad.

Twitter
Dad Jokes
@Dadsaysjokes
What’s the difference between a bowl of moldy lettuce and a depressing song?
One is a bad salad, and the other is a sad ballad.
5:05 PM · Jun 16, 2021·Twitter for iPhone

LaffGaff
Moldy Lettuce
June 23, 2021 by laffgaff
What’s the difference between a bowl of moldy lettuce and a depressing song?
One is a bad salad, and the other is a sad ballad.

“What’s the difference between a bowl of moldy lettuce and a depressing song?” (riddle)