“Why was the cat so small?”/“Because it only ate condensed milk.”

A milk riddle is:
 
Q: Why was the cat so small?
A: Because it only ate condensed milk.
 
The “condensed milk” joke has been cited in print since at least 2003.
 
       
Google Books
Noah’s Favorite Animal Jokes
By Compiled by Barbour Staff
Uhrichsville, OH: Barbour Publishing, Inc.
2003
Pg. ?:
Why was the cat so small?
Because it only ate condensed milk.
 
8 January 2006, Sunday Mail (Glasgow, UK), “Funnies,” pg. 3:
Why was the cat so small?
Because it only ate condensed milk!
 
Google Groups: Pure Gadzooks!
25th April 2006
Jayne Mee
4/25/06
(...)
Q: Why was the cat so small?
A: Because it only ate condensed milk!
     
Twitter
Wallace Wellington
@usermal
Q: Why was the cat so small?
A: Because it only ate condensed milk!
5:47 PM - 6 Jun 2009
   
YouTube
Ok, here is the joke. Why was the cat so small ? Because it on…
botcaster inc. bot
Published on Jan 23, 2016
Why was the cat so small ?
Because it only ate condensed milk !
 
Twitter
Ærchie
@archiearchive
Why was the cat so small?
Because it only ate condensed milk!
7:11 AM - 4 Jan 2018
 
Twitter
Lucky Score
@LuckyScoreNet
Why was the cat so small ?
Because it only ate
condensed milk !
#Joke from #CatJokes in #Jokes, #Humor and #Satire
2:34 PM - 15 Mar 2018