“A plateau is a high form of flattery”

“A plateau is a high form of flattery” (or “A plateau is the highest form of flattery”) is a “flattery” pun that has been printed on many images. “A Plateau is the highest form of flattery” was posted on the newsgroup rec.games.programmer on October 19, 1997. “A plateau is a high form of flattery” was posted on the website Pun of the Day in June 1999.
 
The one-line saying was popularized on many websites in 2002,
       
   
Google Groups: rec.games.programmer
Help! Watcom!
Steve McAndrewSmith
10/19/97
(...)
A Plateau is the highest form of flattery.
   
Pun of the Day
Great One Liners of the Month
Current Positions for June 1999

(...)
5. A plateau is a high form of flattery.
 
13 April 2002, The Post and Courier (Charleston, SC), “Keep on the punny side of life” by Elsa McDowell, pg. 1:
- A plateau is a high form of flattery.
 
Google Groups: alt.humor.puns
Puns of the Weak 04/26/02
Stan Kegel
4/26/02
(...)
A plateau is a high form of flattery. (Jerry Ulett)
 
Google Groups: alt.humor.puns
Puns of the Weak 10/25/02
Stan Kegel
10/27/02
(...)
A plateau is a high form of flattery (Pun of the Day)
   
Google Groups: alt.humor.puns
Puns of the Weak 11/15/02
Stan Kegel
11/15/02
(...)
A plateau is a high form of flattery. (Joan Adams)
 
Google Books
E-Mail Humor
By Louis G. Morton
Victoria, BC: Trafford Publishing
2005
Pg. 6:
A plateau is a high form of flattery.
 
Twitter
Brandon Danger Hill
‏@Gutshot
A plateau is a high form of flattery.
10:36 PM - 29 Sep 2008
 
Twitter
Spills
‏@spillsmusic
#CORNYjoke: Why is imitation like a plateau?
They’re both the highest form of flattery.
10:36 AM - 26 Aug 2009
 
Twitter
José
‏@bebi59
A Plateau is the highest form of flattery.
2:40 PM - 31 Dec 2009
   
Google Books
Once Apun A Time:
A Rich, Historical and Sometimes Earthy Collection of Puns

By Robin Leech
Victoria, BC: FriesenPress
2015
Pg. ?:
A plateau is a high form of flattery.
 
Google Books
Dr. O.K.‘s Wit, Wisdom and Whatever
By Otis LoVette
New York, NY: Page Publishing, Inc.
2016
Pg. ?:
A plateau is a high form of flattery.
   
15 February 2016, News Mail (Bundsberg, Queensland), “Last Laugh,” pg. 11:
How is imitation like a plateau? They’re both the highest form of flattery.
   
14 November 2016, The Advertiser<

(Adelaide, Australia), “The Last Word” by Marty Smith, pg. 20:
Wordplay: A plateau is the highest form of flattery.