“What is crazy and walks along the sides of buildings?”/“A walnut.”

A “walnut” is not a literal “wall nut,” but there’s a riddle:
 
Q: What is crazy and walks along the sides of buildings?
A: A walnut.
 
The joke was posted on Twitter on November 20, 2014.
 
     
Wikipedia: Walnut
A walnut is the nut of any tree of the genus Juglans (Family Juglandaceae), particularly the Persian or English walnut, Juglans regia. Technically a walnut is the seed of a drupe or drupaceous nut, and thus not a true botanical nut. It is used for food after being processed while green for pickled walnuts or after full ripening for its nutmeat. Nutmeat of the eastern black walnut from the Juglans nigra is less commercially available, as are butternut nutmeats from Juglans cinerea. The walnut is nutrient-dense with protein and essential fatty acids.
 
Twitter
Paula Rzig
@PRezig
Q: What is crazy and walks along the sides of buildings?
A: A walnut.
8:34 AM - 20 Nov 2014
 
Twitter
EzmarSyahid
@EzmarS
Q: What is crazy and walks along the sides of buildings?
A: A walnut.
9:17 PM - 21 Nov 2014
 
Twitter
mariana
@joonsmar
Q: What is crazy and walks along the sides of buildings?
A: A walnut.
2:19 PM - 26 Nov 2014
 
Twitter
Sugar N’ Spice
@EatSugarNSpice
What is crazy and walks along the side of buildings? A walnut.
10:05 AM - 14 Oct 2015
     
Twitter
mark stanz
@MarkStanz1
Q: What is crazy and walks along the sides of buildings? A wall nut.
6:37 PM - 7 Aug 2017
 
Twitter
Tony Herget
@T_Hergz
Q: What is crazy and walks along the sides of buildings?
A: A walnut.
8:39 PM - 7 Sep 2017
 
Twitter
lorraine Jo King
@LahLahBean
#tuesdaytitters What is crazy and walks along the side of buildings? A walnut. ☺
5:10 AM - 20 Mar 2018