“Human beings” sounds like “human beans.” A joke was printed in Tit-Bits in 1933:
     
“A teacher, giving a lesson on beans, asked the children to compose sentences containing the word ‘beans.’ The usual bright boy produced ‘My father grows beans,’ and the usual bright girl was ready with ‘My mother cooks beans.’ Then a little one made this effort, ‘We are all human beans.’”
   
The joke has been printed on several images.
   
       
23 May 1933, The Christian Science Monitor (Boston, MA), “In Lighter Vein,” pg. 15, col. 3:
As Some Pronounce
A teacher, giving a lesson on beans, asked the children to compose sentences containing the word “beans.”
 
The usual bright boy produced “My father grows beans,” and the usual bright girl was ready with “My mother cooks beans.”
 
Then a little one made this effort, “We are all human beans.”—Tit-Bits.
   
2 June 1933, Chino (CA) Champion, pg. 3, col. 3:
As Some Pronounce
A teacher, giving a lesson on beans, asked the children to compose sentences containing the word “beans.”
 
The usual bright boy produced “My father grows beans,” and the usual bright girl was ready with “My mother cooks beans.”
 
Then a little one made this effort, “We are all human beans.”—Tit-Bits.
   
Google Groups: rec.humor
Classroom Capers
Dark Shadow
2/21/97
(...)
A teacher asked her class for sentences using the word “beans”.
“My father grows beans,” said one student.
“My father cooks beans,” said another.
Then a third spoke up : “We are all human beans.”
 
Know Your Meme
Human Bean
Updated 3 years ago by Brad Kim.
Added 3 years ago by Molly Horan.
About
“Human Bean” is a common misspelling or mispronunciation of the phrase “human being.” On the web, the grammatical error has given rise to a series of cartoon illustrations and photoshopped images depicting an anthropomorphic bean.
Origin
The phrase was originally used as an intentional misspelling of “human being” in the 1952 children’s novel The Borrowers, in which the miniature humans known as the “borrowers” refer to the average-sized humans as “human beans,” to mimic how young children may mispronounce it. The earliest known satirization of “human bean” as a commonly misspelled word appeared in the webcomic Monkey Business in a strip titled “Human Bean,” published on November 6th, 2003.
 
Reddit—Jokes
We are all human beans
submitted January 29, 2015 by boston2011
A teacher asked her students to use the word “beans” in a sentence. “My father grows beans,” said one girl. “My mother cooks beans,” said a boy. A third student spoke up, “We are all human beans.”
   
Google Books
Food Jokes
By Joe King
Marine Publsihing
2016
Pg. ?:
A teacher asked her students to use the word “beans” in a sentence. “My father grows beans,” said one girl. “My mother cooks beans,” said a boy. A third student spoke up, “We are all human beans.”
 
Reddit—Clean Jokes
A teacher asked her students to use the word “beans” in a sentence… (self.cleanjokes)
submitted January 18, 2018 by Kassandra_Brentley
“My father grows beans,” said one girl. “My mother cooks beans,” said a boy. A third student spoke up, “We are all human beans.”