"A refrigerator is a place where you store leftovers until they are ready to be thrown out” is an old comic observation.

A newspaper comic caption on September 8, 1954 was: “Our refrigerator is full of stuff that’s too old to eat and not old enough to throw out.” Two years later, on September 24, 1956, the full leftover joke appeared: “A refrigerator is a place to store leftovers until they are old enough to throw out.”


8 September 1954, Bridgeport (CT) Telegram, ‘The Neighbors” cartoon by George Clark, pg. 5, col. 3:
“Our refrigerator is full of stuff that’s too old to eat and not old enough to throw out.”

24 September 1956, Indiana (PA) Evening Gazette, pg. 1 (masthead):
A refrigerator is a place to store leftovers until they are old enough to throw out.

Google News Archive
4 October 1956, Warsaw (IN) Times-Union “Little Liz” cartoon caption, pg. 5, col. 2:
A refrigerator is a place to store leftovers until they are old enough to throw out.

Google Books
The New Speaker’s Treasury of wit and Wisdom
By Herbert V. Prochnow
New York, NY: Harper
1958
Pg. 119:
A refrigerator is a place where you store leftovers until they are old enough to throw out. Ogden, Utah, Standard-Examiner

Google Books
20,000 Quips & Quotes
By Evan Esar
New York, NY: Barnes & Noble Books
1995, ©1968
Pg. 318:
A refrigerator is a place where you store leftovers until they are ready to be thrown out.