“You can’t fix stupid” is a popular American expression. “But I can’t fix stupid” was in the comic strip Shoe by Jeff MacNelly (1947-2000) on August 4, 1991. Jim White (1937-2009), an American radio talk-show host on KMOX, in St. Louis, Missouri, frequently used the expression and was credited for it in a newspaper on February 2, 1995, but there is no evidence that he used the expression as early as 1991.
 
American stand-up comedian, actor and author Ron White (no relation to Jim White) nationally popularized “you can’t fix stupid” in 2005 (when he attempted to trademark the term) and 2006 (when it was the title of his book).
 
Sayings from the phrase include “Even duct tape can’t fix stupid,” “Even duct tape can’t fix stupid, but it can muffle the sound,” “They say you can’t fix stupid. Turns out you can’t quarantine it either,” “You can’t fix stupid. Not even with duct tape” and “You can’t fix stupid, but you can vote it out.”
   
     
Wikipedia: James C. White
James Charles White, Jr. (April 6, 1937 – September 2, 2009) was an American radio talk-show host on KMOX, in St. Louis, Missouri.
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Commentary
Some of Jim White’s favorite expressions were:

. “You can’t fix stupid.”
 
Wikipedia: You Can’t Fix Stupid
You Can’t Fix Stupid is an album by American comedian Ron White. It was released by Image Entertainment on February 7, 2006. The album peaked at number 1 on the Billboard Top Comedy Albums chart.
     
Newspapers.com
4 August 1991, Kokomo (IN) Tribune, “Shoe” comic strip by Jeff MacNelly, comic psec., pg.?:
“YO, EUGENE, HOW GOES IT DOWN IN THE PRESSROOM?”
“HORRID! (...) IT’S YOUR EDITORIAL PAGE… (...) I CAN FIX ALMOST ANYTHING THAT RUNS ON THOSE PRESSES. (...) BUT I CAN’T FIX STUPID.”
 
2 February 1995, Journal Gazette (Mattoon, IL), “Readers Write,” pg. A4, col. 3:
A talk show host on radio KMOX in St. Louis, by the Name of Jim White has a bumper sticker you need—“You can’t fix stupid!”
REX OEHM
Mattoon
   
3 April 1995, Honolulu (HI) Advertiser, “Letters,” pg. A9, col. 1:
Fixing positions by quota will never improve qualifications because “you can’t fix stupid.”
MAXINE JACKSON
 
12 May 1995, Daily Tribune (Wisconsin Rapids, WI), “Things My Mother Always Told Me,” pg. 9B, col. 2:
You can’t fix stupid.
Hazel Meyer, Wis. Rapids
 
28 December 1995, St. Louis (MO) Post-Disaptch, “It’s not all that trivial” by Bob Rose, pg. 53:
8. What do the bumper stickers given out by KMOX Radio`s Jim White say?
Answers: 8. You Can’t Fix Stupid;
   
30 January 1996, Nashville (TN) Banner, “Trucking industry penalized for problems caused by others” by Hershel Butts, pg. A6:
When I heard of the passing of this law, I was once again reminded of the words of the famous German philosopher Wolfgang Wirtz, who said: “You can’t fix stupid.”
     
6 October 1996, St. Louis (MO) Post-Dispatch, “Morning Briefing” by Jeff Gordon, pg. 2D:
Concerned reader Cecil Chambers wrote, “The Rams are making the same stupid mistakes and take the same stupid penalties they took last year. I guess Jim White is right. You can’t fix stupid.”
 
24 October 1998, The State Journal-Register (Springfield, IL), ‘Calendar will mark the Year of the Stupid” by Tamara Browning, pg. 8, col. 1:
The couple saw a plaque in a gift shop that read “You just can’t fix stupid.”
     
25 November 2002, The Tennessean (Nashville, TN), “Letters to the Editor,” pg. A10:
Is a tax on stupidity such a bad idea?
To the Editor:
Jim White was an on-air personality on KMOX, the famous St Louis radio station (AM-1120). He had this saying: “You can’t fix stupid.”
(...)
J.H. Curley
Franklin 37064
 
OCLC WorldCat record
Ron White : you can’t fix stupid.
Author: Ron White; Image Entertainment (Firm)
Publisher: [Chatsworth, CA] : Image Entertainment, [©2006]
Edition/Format:   DVD video : English : Widescreen
Summary:
Irreverent bad boy Ron White will crack you up with a nonstop stream of hilarious jokes and clever observations. He explores the pitfalls of marriage, offers some hysterical advice on picking a spouse, and introduces the unforgettable Squirrel Man.
   
YouTube
RonWhite: You Can’t Fix Stupid
Jeff Ravitz
Published on May 30, 2010
Ron White was riding high on his “Tater Salad” DVD when he did this follow-up special for which I designed the lighting. The most famous story is the title piece, “You Can’t Fix Stupid”. We shot the show at the Majestic Theatre in Dallas.
     
Urban Dictionary
you can’t fix stupid
The response to seeing some moron doing something incredibly asinine.
Eric has a poisonous pet albino monocled cobra as pet. It bit him and almost killed him.
You can’t fix stupid.
#dumb#stupid#asinine#moron#dope
by kajoe February 01, 2011
 
(Trademark)
Word Mark YOU CAN’T FIX STUPID
Goods and Services (CANCELLED) IC 041. US 100 101 107. G & S: Entertainment services in the nature of live and televised performances by a comedian. FIRST USE: 20050722. FIRST USE IN COMMERCE: 20050722
Standard Characters Claimed
Mark Drawing Code (4) STANDARD CHARACTER MARK
Serial Number 78778224
Filing Date December 21, 2005
Current Basis 1A
Original Filing Basis 1A
Published for Opposition August 29, 2006
Registration Number 3171309
Registration Date November 14, 2006
Owner (REGISTRANT) White, Ron INDIVIDUAL UNITED STATES Penthouse c/o Fox Law Group 14724 Ventura Boulevard Sherman Oaks CALIFORNIA 914033513
Attorney of Record Stanley W. Sokoloff
Type of Mark SERVICE MARK
Register PRINCIPAL
Live/Dead Indicator DEAD
Cancellation Date June 21, 2013