"When someone tells you nothing is impossible, ask…

“When someone tells you nothing is impossible, ask him to dribble a football” is a saying that has been printed on several images. The saying has been cited in print since at least 1979 and is of unknown authorship.

8 February 1979, Sentinel Star (Orlando, FL), “Hush Puppies” by Charles Wadsworth, pg. 6B, col. 2:
OVERHEARD: The next time someone tells you that nothing is impossible, ask them to dribble a football.

13 May 1979, Plano (TX) Daily Star-Courier, “Out’s Bounds” by Ed Voss, sec. 1, pg. 12, col. 1:
When someone tells you that nothing is impossible—ask him to dribble a football.

24 June 1979, Arkansas Gazette (Little Rock, AR), “Jokes: Bob Steele on the Air,” Parade magazine, pg. 33, col. 4:
When somebody tells you that nothing is impossible, ask them to dribble a football.

Google Books
Today’s Chuckle:
2500 Great One-Liners for Every Occasion
By Paul Harlan Collins
New York, NY: Perigree Books
1993
Pg. 98:
Next time someone tells you nothing is impossible, ask him to dribble a football.

Google Groups: de.newusers.questions
Fido !
Leif Juergensen
1/4/95
(...)
When someone says nothing is impossible, ask him to dribble a football.

Google Groups: ont.general
Help Save a Man’s Life
David C. Wright
10/9/95
(...)
When somebody says nothing is impossible, ask him to dribble a football

Google Groups: alt.fan.mike-jittlov
WoSaT CD?
Laseroo
8/14/99
(...)
“Those who say nothing is impossible have never tried to dribble a football”

Twitter
Nicolas M. Leon‏
@nicolasleon
When somebody tells you nothing is impossible, ask him to dribble a football.
3:49 PM - 15 Jul 2008

Twitter
moswald‏
@moswald
When somebody tells you nothing is impossible, have him dribble a football.—Unknown
10:20 AM - 6 Aug 2008

Google Books
The Capitalist Spirit:
How Each and Every One of Us Can Make A Giant Difference in Our Fast-Changing World
By Yale Hirsch
Hoboken, NJ: John Wiley & Sons, Inc.
2010
Pg. 206:
When somebody tells you nothing is impossible, ask him to dribble a football. — Anonymous

Google Books
The Little Book of Humorous Quotes
Edited by Malcolm Kushner
The Little Quote Books
2011
Pg. ?:
When somebody tells you nothing is impossible, ask him to dribble a football . ~Author Unknown