A prank (sometimes done on April 1st, April Fools’ Day) is eating vanilla pudding from a mayonnaise jar. “People give you the weirdest looks when you’re gobbling up heaping spoonfuls of vanilla pudding from a mayonnaise jar” was posted on Twitter on March 23, 2009. “Mayo/Pudding Switch - April Fools” was the title of a YouTube video on April 1, 2011.
 
“TO DO LIST: Make vanilla pudding. Put in mayo jar. Eat in public” was posted on the website Grouchy Rabbit on June 29, 2011. The prank has been printed on several images.
 
         
Twitter 
Reluctant Human
@Zaius13
People give you the weirdest looks when you’re gobbling up heaping spoonfuls of vanilla pudding from a mayonnaise jar. nom nom what? nom nom
12:56 AM - 23 Mar 2009
 
YouTube 
Mayo/Pudding Switch - April Fools
Published on Apr 1, 2011
A prank I played on my wife for April Fools 2011.
   
Twitter
Paul Young
@ThatBigPY
Replying to @painterm
@painterm empty out a mayonnaise jar and fill it with vanilla pudding and walk around outside eating it.
1:26 PM - 1 Apr 2011
     
Twitter
JJ
@fighter419
To do list Make vanilla pudding. Put in mayo jar. Eat in public
3:21 PM - 29 Jun 2011
 
Twitter
Raine
@dorkishmuffin
To do list: Make vanilla pudding. Put in mayo jar. Eat in public. http://e.ht/J5
9:59 PM - 29 Jun 2011
 
Twitter
Susan Grove
@SusanAGrove
Random thing to do: fill a mayonnaise jar with vanilla pudding and eat it in public.
8:34 PM - 3 Jul 2011
 
Google Groups: alt.buddha.short.fat.guy
To do
Nobody in Particular
4/16/12
(...)
The rest is kinda lame, like:
 
Make vanilla pudding. Put in mayo jar.  Eat in public.
     
YouTube
Eating Mayo in Public Prank (BreakingNormalProd)
BreakingNormalProd
Published on Sep 12, 2013
We decided to do a more classic prank. Vanilla pudding in a mayo jar. This actually turned out better than expected! NEW VIDEOS EVERY THURSDAY!!
 
11 March 2015, Philadelphia (PA) Inquirer, “DeVido,” pg. C2, col. 2:
1. Make Vanilla Pudding. Put in Mayo Jar. Eat in Public.
     
Google Books
Shaun the Sheep:
Pranks a Lot!
By Martin Howard
Somerville, MA: Candlewick Entertainment
2016
Pg. ?:
SICKENING SPOONFUL
Carefully clean out a mayonnaise jar after it has been used up. Put some vanilla pudding or yogurt into the jar instead. Then make sure someone is watching when you proceed to spoon it up and eat it.
 
April 2016, Highlights for Children, “Easy April Foolery” by Allison Kane, pg. 32:
Save an empty mayonnaise jar and fill it with vanilla pudding. Wait until there are people around, then scoop some of the pudding from the jar into a bowl and dig in. Pretend not to notice the horrified looks from your audience.
 
Twitter
Hot Pickle Surprise
@MikoSquiz
Replying to @scruff @PupWhiskey
It’s like the old “eating hummus or vanilla pudding out of a mayonnaise jar on public transport” trick.
4:13 PM - 28 Feb 2018
 
Reddit—Dad Jokes
Does anyone else here eat vanilla pudding out of a mayonnaise jar? (self.dadjokes)
submitted March 1, 2018 by Boom223