"If it weren’t for caffeine, I’d have no personality whatsoever” is a jocular saying about coffee drinkers. The saying has been cited in print since at least 2001 and is of unknown authorship.


Yahoo! Groups: avenger-sfi
“Carlos & Heidi”
Sun Jul 29, 2001 12:10 am
(...)
If it weren’t for caffeine I’d have no personality whatsoever.
- Unknown

2 November 2002, The Gazette (Colorado Springs, CO), “The Buzz: Talk, tidbits & trivia”:
“If it weren’t for caffeine, I’d have no personality whatsoever.” (Unknown)

Google Books
Communication Wins
By Steve Hartkopf
Bloomington, IN: AuthorHouse
2009
Pg. 35:
If it weren’t for caffeine I’d have no personality whatsoever! - Anonymous

Washington (DC) Post—ComPost blog
Caffeine killer? Never! The Starbucks defense
By Alexandra Petri | September 21, 2010; 1:21 PM ET
Caffeine makes you psychotic? That’s troubling! In the words of my friend and eminent Canadian Adam Goldenberg, “If it weren’t for caffeine, I’d have no personality whatsoever.”

Google Books
Fundamentals of Abnormal Psychology (6th edition)
By Ronald J. Comer
New York, NY: Worth Publishers
2011
Pg. 74:
“If it weren’t for caffeine, I’d have no personality whatsoever.”—Anonymous