“The show must go on” is a show business adage from the 1860s. “The show must go wrong” is a variation of the saying that became popular in the 2000s.

“The Show Must Go Wrong” was an episode of the American animated television series Brandy & Mr. Whiskers that aired on July 22, 2005.  The American television sitcom Parks and Recreation, on an episode titled “Freddy Spaghetti” that aired on May 20, 2010, contained the line:
 
“There’s an old saying in show business: The show must go wrong. Everything always goes wrong, and you just have to deal with it.”
 
   
IMDb (The Internet Movie Database) 
Brandy & Mr. Whiskers: Season 1, Episode 38
The Show Must Go Wrong (22 Jul. 2005)
TV Episode |  TV-Y |  30 min |  Animation, Comedy, Family
 
Twitter
Team Follow Back
‏@teamf0ll0wback
the show must go wrong
3:22 AM - 31 Mar 2010
     
Wikia: Parks and Recreation
“Freddy Spaghetti” is the twenty-fourth episode of Season 2 of the NBC television series Parks and Recreation. It originally aired on May 20, 2010 to 4.55 million viewers.
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Quotes
Andy: There’s an old saying in show business: The show must go wrong. Everything always goes wrong, and you just have to deal with it.
 
Twitter
Carter Dotson
‏@wondroushippo
“There’s an old saying in show business, ‘The show must go wrong’” #ParksAndRec
7:51 PM - 20 May 2010
 
Twitter
Lola
‏@LolaGeek
“There’s an old saying in show business, the show must go wrong. Everything always goes wrong and you just have to deal w/ it.” #ParksAndRec
7:51 PM - 20 May 2010
 
Amazon.com
The Show Must Go Wrong (A Jake Russo Mystery Book 4) Kindle Edition
by Phil Edwards (Author)
Product Details
File Size: 584 KB
Print Length: 259 pages
Page Numbers Source ISBN: 1470024608
Publisher: Harrison-Mills Media (February 2, 2012)
Publication Date: February 2, 2012
Sold by: Amazon Digital Services, Inc.
Language: English