“Eat my shorts!” is a saying that has been printed on many images. The saying is similar to “Kiss my ass!” and “Eat shit!”
 
“Eat my shorts” was printed in The Daily Utah Chronicle (University of Utah, Salt Lake City, UT) on November 7, 1972. “Eat my shorts” was said in the movie The Breakfast Club (1985). On the “Bart the Genius” episode (original airdate January 14, 1990) of the animated television sitcom The Simpsons, Bart Simpson said “Eat my shorts!” for the first time.
   
It’s not known who originally authored the “eat my shorts” expression.
 
         
Simpsons Wiki
“Eat my shorts!” is one of Bart Simpson’s trademark catchphrases. Bart uses it to express his rebellious attitude, usually towards authority figures. He pulls his shorts down, and shakes his butt at people, simply to offend them.
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The real history behind the phrase is that Nancy Cartwright, Bart’s voice actor, improvised the line during a table read. She first said it as a prank when she was in her high school marching band at Fairmont High School. The band was supposed to chant, “Fairmont West! Fairmont West!” Instead, she and the entire band chanted, “Eat my shorts! Eat my shorts!” Thus, an icon in popular culture was born.
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There has been speculation that Matt Groening got this phrase from the stoner rebel John Bender in The Breakfast Club. In Futurama there is also a mischievous character by the name of Bender. The phrase “Don’t have a cow” appears in another John Hughes film, Sixteen Candles. “Eat my shorts!” is also exclaimed by a main character in Stephen King’s 1986 movie “Maximum Overdrive”, coincidentally starring Yeardley Smith.
       
7 November 1972, The Daily Utah Chronicle (University of Utah, Salt Lake City, UT), “Letters to the Editor: Accurate picture,” pg. 4, cols. 1-2:
The first allegation is that of TKE yelling obscenities at the Chronicle staff. This is false. Yes, TKE did respond mockingly to the Chronicle cheers, as did James Waldo, himself, with a string of “Eat My Shorts,” through a megaphone, several times.
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Gordon Wilkinson, Chaplain
Tau Kappa Epsilon
   
18 April 1973, Ligonier (PA) Echo, The Ram Page, pg. 5, col. 8 classified ad:
To whom it may concern:
Eat my shorts. They’re free.
 
14 January 1974, The Daily Utah Chronicle (University of Utah, Salt Lake City, UT), “Message from Garcia” by Robert Garcia, pg. 4, col. 3:
Eat My Shorts by Euell Gibbons. Yes, Fruit-of-the-Loom is edible and makes a delicious dessert. Mr Gibbons is barely palatable.
 
31 May 1976, Chicago (IL) Tribune, “Top drawer idea—snacking on skivvies” by Charles Leroux, sec. 2, pg. 6, col. 2:
“Eat my shorts.”
(A product called “Candypants.”—ed.)
     
August 1976, Vogue (New York, NY), “People Are Talking About” by Leo Lerman, pg. 137, col. 2:
The re-place for “drop dead!”: “Eat my shorts!”
 
4 November 1976, The Daily Northwestern (Evanston, IL), ‘What’s in a name, For IM teams, imagination” by Alice Crancer, pg. 8, col. 1:
CASEY FOX, the captain of a team named Eat My Shorts, said “We wanted a distinctive name for our football team. A lot of guys in the Fiji house use the expression a lot. We thought we’d do something offbeat and crazy and off our minds.”
   
Google Books
The Boys from the Dome:
Folklore of a Modern American Male Group
By James P Leary
thesis, Indiana University
1977
Pg. 69:
Appropriate to gigs as well as everyday conversation were jokingly abusive formularized interchanges. Notre Dame boys greeted one another with “Eat It” to be answered by “Eat It Raw” or “Eat a Big One” or “Eat My Shorts,” sometimes “Eat My Crusty Shorts.”
 
IMDb (The Internet Movie Database)
The Breakfast Club (1985)
Quotes
Richard Vernon: You’re not fooling anyone, Bender. The next screw that falls out will be you.
John Bender: Eat my shorts.
Richard Vernon: What was that?
John Bender: Eat… My… Shorts.
Richard Vernon: You just bought yourself another Saturday.
 
OCLC WorldCat record
Eat my shorts
Author: Bill Bernico
Publisher: Cleveland, WI : Downwind Books, 1998.
Edition/Format:   Print book : Fiction : English
     
Urban Dictionary
Eat My Shorts food
As in the movie ‘The Breakfast Club’, another way to say “Eat my shit!”
Bender (to Vernon): Eat my shorts!
by DiveInPuddles8 July 05, 2003
 
OCLC WorldCat record
Eat my Shorts! Soziale und politische Kritik in “Die Simpsons”
Author: Wolf-Dietrich Nehlsen; Sebastian Hübers; Wiebke Wolter
Publisher: München Science Factory 2013
Edition/Format:   eBook : Document : German : 1. Auflage
   
Mental Floss
8 Slang Terms from The Breakfast Club, Decoded
BY ANGELA TUNG MARCH 24, 2017
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4. EAT MY SHORTS
While this euphemism for “eat my shit” may seem quintessential Bart Simpson, it’s uttered by Bender in The Breakfast Club two years before The Simpsons makes its premiere on The Tracey Ullman Show. Even earlier is a (pretty funny) 1984 song called “Eat My Shorts” by comedian and radio personality Rick Dees.
 
The phrase comes full circle when on Futurama, Bender the robot—who, by the way, was named by show creator Matt Groening for The Breakfast Club’s John Bender—finds a Bart Simpson doll which says “Eat my shorts!” Bender obliges.