“Whenever I see a sign that says ‘keep off the grass,‘I wonder how it got there”

A joke about “keep off the grass” signs is:
   
“Whenever I see a sign saying ‘keep off the grass’, I often wonder how it got there.”
 
That is, someone must have walked on the grass to put the sign up. The jocular one-line saying was posted on Twitter on May 8, 2013.
 
 
Twitter
Jamie Macgregor
‏@m1ndspeak5truth
whenever I see a sign saying ‘keep off the grass’, I often wonder how it got there
3:49 PM - 8 May 2013
 
Twitter
Colin
‏@Colin_1234
Grass: I saw a sign today day telling please keep off the grass. I wonder how it got there?The post Grass appe… http://bit.ly/16dN4w6
1:07 AM - 15 May 2013
 
Twitter
your girl
‏@biebsxrauhl
@LittlecBeadles i saw a sign today that said “keep off grass.” I wonder how it got there. #imadechristianlaugh
10:08 PM - 23 May 2013
 
Twitter
✌SuperSpiddy ✌
‏@Spider_Pig_619
whenever I see a sign saying ‘keep off the grass’, I often wonder how it got there
3:50 PM - 8 May 2013
 
Twitter
Crap Jokes
‏@TheCrapJoker
Whenever I see a sign that says ‘keep off the grass’..
I wonder how it got there.
6:15 AM - 20 Apr 2015
 
Twitter
It’s Me!!
‏@PSecure4u
I saw a sign today day telling please keep off the grass. I wonder how it got there?
9:07 AM - 5 Aug 2016