“I think adults are just children who owe money” was said in the movie Peter’s Friends (1992). “Adults are just kids who owe money” has been cited in print since at least 1998 and 1999. The jocular saying has been printed on many gift items, such as bumper stickers and posters.
 
“Adults are just kids who owe money” is a realistic twist on the original saying—“Adults are just kids with money.”
 
 
The Internet Movie Database
Memorable quotes for
Peter’s Friends (1992)
Andrew: I think adults are just children who owe money.
 
Google Books
Kids Say the Darndest Things
By Bill Cosby
New York, NY: Bantam Books
1998
Pg. 3:
Art knew that adults are just kids who’ve lost their way, just kids who owe money and who’ve stopped saying what they really think.
 
Greenspun.com
Adults are just kids who owe money.
(...)
—gobbles (.(JavaScript must be enabled to view this email address)), February 11, 1999
     
Goofball.com
Sayings that should be on buttons…
By: Robnoxious
Published: 03/22/1999
(...)
Adults are just kids who owe money.
 
Google Books
Key West Graffiti
By W.J. Tolien
Buffalo, NY: Thorner Press
2001
Pg. 28:
Adults are just kids who owe money.
 
15 February 2004, The Post-Standard (Syracuse, NY), pg. C-5, col. 1:
Bumper sticker
ADULTS ARE JUST KIDS WHO OWE MONEY