A walnut riddle has been cited in print since at least 2004:

Q: How do you make a walnut laugh?
A: Crack it up!

A version including Brazil nuts was posted on Twitter by Lorraine Jo King on August 27, 2021:

Q: What’s the best way to get walnuts and Brazil nuts to laugh?
A: Crack them up.


Wikipedia: Walnut
A walnut is the nut of any tree of the genus Juglans (family Juglandaceae), particularly the Persian or English walnut, Juglans regia.

A walnut is the edible seed of a drupe, and thus not a true botanical nut. It is commonly consumed as a nut. After full ripening for its edible seed when the shell has been discarded, it is used as a garnish or a snack.

Google Groups: alt.humor.puns
Kids Puns of the Weak 06-29-04
Stan Kegel
Jun 30, 2004, 2:33:13 AM
(...)
How do you make a walnut laugh?
Crack it up! (Neeshe,12)

Newspapers.com
25 August 2005, Newsday (Long Island, NY), pg. C18, col. 4:
How do you make a walnut laugh?
Crack it up.
Amber Robinson
AGE 11,
EAST PATCHOGUE

Google Books
The Mammoth Book of Really Silly Jokes:
Humour for the whole family
Edited by Geoff Tibballs
London, UK: Constable & Robinson Ltd
2011
Pg. ?:
How do you make a walnut laugh?
Crack it up.

Google Books
101 Amazing Food Jokes
By Jack Goldstein
Andrews UK Limited
2013
Pg. ?:
How do you make a walnut laugh?
Crack it up!

Twitter
Jenny Westerkamp, RD, CSSD
@JennyWesterkamp
How do you make a walnut laugh?...you crack it up!!!! Also eat walnuts. They look like brains + help your brain. Bye bye.
((Thx @amyxvu!))
9:27 AM · Sep 18, 2013·Twitter for iPhone

Twitter
Kayyteee
@katembrown013
How do walnuts laugh?
They crack up!
#dailyjokesifindonmydesk
9:36 PM · Mar 3, 2014·Twitter for iPhone

Twitter
DeRuosi Nut
@DeRuosiNut
How do you make a walnut laugh? Crack it up. #happymonday #walnuts
12:28 PM · Mar 24, 2014·Twitter Web Client

Twitter
James Creelman
@James_Creelman
hi @RealKidsJokes Why do walnuts laugh at nutcrackers? Because they crack them up.
1:08 AM · May 4, 2017·Twitter Web Client

Twitter
California Walnuts
@Walnuts_UK
How do you make a walnut laugh?....Crack it up Send us your best walnut jokes!
11:49 AM · Jan 15, 2018·Hootsuite

Twitter
Lorraine Jo King
@lahlahbean
#badjokefriday
What’s the best way to get walnuts and Brazil nuts to laugh?
Crack them up.
2:04 AM · Aug 27, 2021·Twitter for iPhone