“What kind of fish goes well with peanut butter?”/“A jellyfish.”

A peanut butter and jelly riddle is:
 
Q: What kind of fish goes well with peanut butter?
A: A jellyfish.
 
The joke has been cited in print since at least 1974. 
 
“I bet jellyfish are sad that there are no peanut butter fish” is related saying.
     
       
5 October 1974, Chippewa Herald (Chippewa Falls, WI), “Riddle Me This,” kids’ page:
Q: What is the best fish to eat with peanut butter?
A: A jellyfish.
Charlene Bowe, 7th Grade
Chippewa Falls, Wisconsin
 
22 February 1975, The Evening Standard (Uniontown, PA), “My Favorite Jokes” by Tomy Friend, Uniontown, pg. 18, col. 2:
Q. What kind of fish goes good with peanut butter?
A. Jellyfish.
 
24 September 1989, Newsday (Long Island, NY), ““Smiles,” Kidsday sec., pg. 1:
What kind of fish goes with peanut butter?
Joke Answer: Jellyfish. - Robyn Etheridge, Massapequa
   
Google Books
The Penguin’s put-downs, jokes and riddles
By Scott Franklin and Batton Lash
New York , NY T. Doherty
1992
Pg. 105:
What fish does The Penguin love to eat with peanut butter?
Jellyfish!
   
Google Books
Teaching Elementary Language Arts:
An Integrated Approach
By Dorothy Rubin
Boston, MA: Allyn and Bacon
1995
Pg. 220:
What fish goes well with peanut butter?
jellyfish
 
Reddit—Jokes
Fish jokes
submitted July 11, 2011 by hornytoad69
(...)
What kind of fish goes great with peanut butter? A jellyfish.
     
Google Books
Amusing Animal Jokes to Tickle Your Funny Bone
By Amelia LaRoche
Berkeley Heights, NJ: Enslow Elementary, an imprint of Enslow Publishers, Inc.
2015
Pg. 17:
What do sharks eat with peanut butter?
Jellyfish.
 
Reddit—Jokes
What fish tastes great with peanut butter?
submitted January 24, 2016 by kevinnetter
Jellyfish
 
Reddit—Dad Jokes
What kind of fish goes with peanut butter? (self.dadjokes)
submitted September 4, 2018 by mikeyD_
A jellyfish