“Funny beast” and “bunny feast” are included in several jokes.
 
“Q: What is the difference between a unicorn and a large lettuce? A: One is a funny beast and the other is a bunny’s feast” was printed in The Sun-Herald (Sydney, New South Wales) on May 11, 1997. “What’s the difference between a unicorn and lettuce? One is a funny beast, and the other is a bunny feast. (Lederer & Ertner)” was posted on the newsgroup alt.humor.puns on November 22, 2002. “What’s the difference between a unicorn and a lettuce? – One is a funny beast, the other is a bunny feast” was printed in the book Two Nuns In A Bath (2009) by Geoff Tibballs.
   
“HEY! What is the difference between bigfoot and lettuce? One’s a funny beast and the other is a bunny feast! HAHAHAHAHAHAHA!” was posted on Twitter by Annoying Orange on August 17, 2010. “What’s the difference between an elephant and a large lettuce? One’s a funny beast, the other is a bunny feast” was printed in the book The Mammoth Book of Really Silly Jokes (2011) by Geoff Tibballs.
   
“Q: What’s the difference between a duck-billed platypus and a bowl full of lettuce?  A: One is a funny beast and the other is a bunny feast” was printed in the book Wild-and-Woolly Animal Jokes: An Untamed Collection of the World’s Best Animal Humor (2012) by David McLaughlan. “what is the difference between a platypus and a head of lettuce? one is a funny beast, and the other is a bunny feast” was posted on Twitter by purpletrice on January 30, 2019.
 
“What’s the difference between a unicorn and a carrot? One’s a funny beast and one’s a bunny feast” was posted on Twitter by Stephanie Ng on July 14, 2014. “What is the difference between a unicorn and a carrot? One is a funny beast and the other is a bunny feast” was posted on Reddit—Jokes on February 21, 2019. “What’s the difference between a unicorn and a carrot? One is a funny beast, the other is a bunny feast” was posted on Reddit—Dadjokes on August 22, 2022.
   
             
Newspapers.com
11 May 1997, The Sun-Herald (Sydney, New South Wales), Super Scene, pg. 7, col. 4:
Q: What is the difference between a unicorn and a large lettuce?
A: One is a funny beast and the other is a bunny’s feast.
Patrice (10) Berkeley Vale.
 
Google Groups: alt.humor.puns
Puns of the Weak 11/22/02
Stan Kegel
Nov 22, 2002, 11:01:21 PM
(...)
What’s the difference between a unicorn and lettuce?
One is a funny beast, and the other is a bunny feast. (Lederer & Ertner)
     
Google Groups: alt.humor.puns
Puns of the Weak 06-27-03
Stan Kegel
Jun 27, 2003, 11:00:49 PM
(...)
What is the difference between a unicorn and lettuce ?
One is a funny beast and the other is a bunny feast. (Jim Ertner)
     
Google Groups: alt.religion.rabbet
Humor from the Net
Bill McCray
Jul 6, 2003, 3:15:26 PM
PUNS OF THE WEAK for the week ending July 19, 2002, part 5
(...)
What is the difference between a unicorn and a large head of
lettuce?
One is a funny beast and the other a bunny feast.
(Michael Johnstone)
     
Google Books 
Two Nuns In A Bath
By Geoff Tibballs
London, UK: Constable & Robinson Ltd
2009
Pg. ?:
What’s the difference between a unicorn and a lettuce? – One is a funny beast, the other is a bunny feast.
   
Twitter
Clark Tucker
@Astroranger
RT @GuitarDragon: What is the difference between a unicorn and lettuce? One is a funny beast and the other is a bunny feast.
11:23 PM · Jul 11, 2009·Twitter Web Client
   
Twitter
Annoying Orange
@annoyingorange
HEY! What is the difference between bigfoot and lettuce? One’s a funny beast and the other is a bunny feast! HAHAHAHAHAHAHA!
12:39 PM · Aug 17, 2010·Twitter Web Client
 
Google Books
The Mammoth Book of Really Silly Jokes
Edited by Geoff Tibballs
London, UK: Constable & Robinson Ltd
2011
Pg. ?:
What’s the difference between an elephant and a large lettuce?
One’s a funny beast, the other is a bunny feast.
   
Google Books
Wild-and-Woolly Animal Jokes:
An Untamed Collection of the World’s Best Animal Humor
By David McLaughlan
Uhrichsville, OH: Barbour Publishing, Inc.
2012
Pg. ?:
Q: What’s the difference between a duck-billed platypus and a bowl full of lettuce?
A: One is a funny beast and the other is a bunny feast.
       
Twitter
Stephanie Ng
@_stephanihao
What’s the difference between a unicorn and a carrot?
One’s a funny beast and one’s a bunny feast.
12:15 AM · Jul 14, 2014·Twitter Web Client
   
Twitter
Horny Pony
@horny_pony_
What is the difference between a #unicorn and a carrot? One is a funny beast and the other is a bunny feast.
11:17 AM · Oct 28, 2014·Twitter for iPhone
 
Twitter
Fortitude J B Huddlebeck
@clagsborough
What’s the difference between a duck-billed platypus and a lettuce? A platypus is funny beast whereas a lettuce is a bunny feast!
5:40 AM · Aug 16, 2015·Twitter Web Client
   
Twitter
purpletrice
@martrice_cpa
what is the difference between a platypus and a head of lettuce?
one is a funny beast, and the other is a bunny feast.
#JokeoftheDay
8:13 AM · Jan 30, 2019·Twitter for Android
 
Reddit—Jokes
Posted by u/[deleted] February 21, 2019
What is the difference between a unicorn and a carrot?
One is a funny beast and the other is a bunny feast.
   
Reddit—Showerthoughts
Posted by u/Chickenblood69 April 4, 2019
A unicorn is a funny beast and a carrot is a bunny feast…
     
Reddit—Jokes
Posted by u/SundaySchoolBilly August 28, 2019
What’s the difference between a head of lettuce and a unicorn?
One is a funny beast, and the other is a bunny feast!
   
Reddit—Jokes
Posted by u/SundaySchoolBilly March 20, 2020
What’s the difference between a unicorn and a head of cabbage?
One is a funny beast, and the other is a bunny feast!
 
Reddit—Teenagers
Posted by u/[deleted] March 13, 2021
What’s the difference between between a unicorn and a lettuce
Ones a funny beast and the other is a bunny feast
 
Reddit—Teenagers
Posted by u/[deleted] May 19, 2021
(...)
What’s the difference between between a unicorn and a lettuce? Ones a funny beast and the other is a bunny feast
 
Reddit—Dadjokes
Posted by u/pvsocialmedia August 22, 2022
What’s the difference between a unicorn and a carrot?
One is a funny beast, the other is a bunny feast.