Cupcakes are often compared to muffins, and frosting is a key difference. “Muffins are (just) bald cupcakes” (or “A muffin is a bald cupcake”) is a saying that has been printed on many images.
   
“A muffin is a bald cupcake” (from stand-up comedian Jim Gaffigan) was printed in the Columbus (OH) Dispatch on March 11, 2006. “You know the difference between a cake and a muffin? Nothing. A muffin is a bald cupcake” (from Jim Gaffigan) was printed in the National Post (Toronto, ON) on January 9, 2008. “A muffin is a bald cupcake and we know it” was posted on Twitter by ssharonrose on February 6, 2008. “A muffin is a bald cupcake” was posted on Reddit—Showerthoughts on December 1, 2019.
 
“everyone knows muffins are really bald cupcakes” was posted on Twitter by KNOWN Creative on May 31, 2008. “muffins are just bald cupcakes” was posted on Twitter by Janet Reid on August 21, 2008. “muffins are BALD cupcakes” was posted on Twitter by ashley ⚰️🏃🏻 on June 28, 2009. “Muffins are bald cupcakes” was posted on Reddit—Showerthoughts on June 11, 2021.
   
“Cupcakes are just frosted muffins” and “Muffins are just unfrosted cupcakes” are related sayings.
     
 
Wikipedia: Jim Gaffigan   
James Christopher Gaffigan (born July 7, 1966) is an American stand-up comedian, actor, writer, and producer. His material often addresses fatherhood, laziness, food, religion, and general observations. He is regarded as a “clean” comic, using little profanity in his routines.
     
11 March 2006, Columbus (OH) Dispatch, “Food jokes served as tasty morsels” by Gary Budzak, pg. 5D:
“He talks a lot about food,” Jim Gaffigan said of himself after telling another joke about food in the first of two “Beyond the Pale” shows he performed last night in the Riffe Center’s Capitol Theatre.
(...)
Gluttonous epigrams abounded: “Packaging is like the clothing of food.” “A muffin is a bald cupcake.” “Steak is like the tuxedo of meat.”
 
Newspapers.com
9 January 2008, National Post (Toronto, ON), “Gaffigan’s Riffs,” pg. AL5, col. 3:
You know the difference between a cake and a muffin? Nothing. A muffin is a bald cupcake.
   
Twitter
ssharonrose
@ssharonrose
A muffin is a bald cupcake and we know it.
7:23 PM · Feb 6, 2008·Twitter SMS
 
Twitter   
KNOWN Creative
@KNOWNnyc
ooooh.  now blackberry cheesecake muffins for church tomorrow!  everyone knows muffins are really bald cupcakes
10:04 PM · May 31, 2008·Twitter Web Client
     
Twitter
Mark Morowczynski
@markmorow
Replying to @cxi
@CXI Sounds like someone is watching Jim Gaffigan. A muffin is just a bald cupcake.
8:57 PM · Feb 1, 2009·Twitter Web Client
 
Twitter
Janet Reid
@Janet_Reid
Replying to @jayewells
@jayewells oh dear god that cake url was rich! “muffins are just bald cupcakes”!!!!
12:02 PM · Aug 21, 2008·Twitter Web Client
   
Twitter
BONFIGLIO
@bbonfiglio
Muffins are just bald cupcakes! in Anaheim, CA http://loopt.us/kC7zzg
12:33 AM · Nov 8, 2008·Twitter Web Client
   
Twitter
Lisa Smith
@lisalisaksmith
Replying to @crossmark
@crossmark “Muffins are just BALD cupcakes, AND YOU KNOW IT!”
12:41 PM · Dec 15, 2008·Twitter Web Client
   
Twitter
ashley ⚰️🏃🏻
@phoenixsorceres
“muffins are BALD cupcakes.”
11:33 PM · Jun 28, 2009·Twitter Web Client
   
Twitter
Black Jedi Terrance
@jedi_terrance
“Muffins are just bald cupcakes”- Jim Gaffigan
12:23 AM · Jul 26, 2010·Echofon
   
Twitter
Evan Bates
@effinevn
“Muffins are bald cupcakes. And we all know it…”-Jim Gaffigan
4:47 PM · Apr 6, 2011·Twitter SMS
 
Twitter       
Chloe Bennet
@chloebennet
Revelation: muffins are bald cupcakes.
10:10 PM · Aug 14, 2014·Twitter for iPhone
 
Reddit—Showerthoughts
Posted by u/EatingHerBooty69 December 1, 2019
A muffin is a bald cupcake.
 
Reddit—Showerthoughts
Posted by u/kactusdaisy June 11, 2021
Muffins are bald cupcakes
 
Reddit—Showerthoughts
Posted by u/Ihatemornings434 June 15, 2022
Muffins are bald cupcakes