“If you shoot a mime, should you use a silencer?” is a jocular one-liner that American stand-up comedian Steven Wright used in his act since at least 1986. “Do you need a silencer if you are going to shoot a mime?” is the form that the saying took by at least 1993, when it was included with similar questions in a much-reprinted grouping titled “Why Ask Why.”
 
           
Wikipedia: Steven Wright
Steven Alexander Wright (born December 6, 1955) is an American stand-up comedian, actor, writer, and Oscar-winning film producer. He is known for his distinctly lethargic voice and slow, deadpan delivery of ironic, philosophical and sometimes nonsense jokes, paraprosdokians, non sequiturs, anti-humor, and one-liners with contrived situations.
     
23 May 1986, The Daily Northwestern (Evanston, IL), “Laugh-in: Wright pleases Cahn crowd despite interference” by Laura Goldberg, pg. 3, col. 2:
He (Steven Wright—ed.) continued firing off one-liners and questions such as, “If you shoot a mime, should you use a silencer?” and “My school colors were clear.”
 
6 December 1987, Sunday News Journal (Wilmington, DE), “On the tube,” pg. K8, col. 4:
“If you shoot a mime, should you use a silencer?”
(From Steven Wright.—ed.)
 
Google Groups: rec.arts.movies
Room With a View  
james cook
6/15/89
(...) 
if you shoot a mime do you need a silencer?    Steven Wright
     
Google Books
The Quotable Quote Book
By Merrit Malloy and Shauna Sorensen
New York, NY: Carol Publishing Group
1990
Pg. 232:
If you shoot a mime, should you use a silencer?
Stephen Wright
 
12 December 1992, Edmonton (Alberta) Journal, “Comic-strip creator brings humor to workplace; Laughter good medicine for stress, he says” by Gordon Cope, pg. C6:
Exploit exaggeration, word-play and disjointed logic to create absurd notions. Adams quotes standup comic Steve Wright’s classic line: “Do you need a silencer to shoot a mime?”
   
Google Groups: comp.parallel
A bit of humor for your holiday enjoyment….
Steve Stevenson-Moderator
11/24/93
Subj:  WHY ASK WHY
(...)
Do you need a silencer if you are going to shoot a mime?
 
11 December 1994, Rocky Mount (NC) Telegram, “Some questions to ponder” by Jeff Herrin, pg. 6A, col. 2:
Do you need a silencer if you are going to shoot a mime?
     
10 March 1995, Northwest Florida Daily News (Fort Walton Beach, FL), “Please don’t break this chain,” pg. B1:
The chain directive is called ``Why Ask Why,’’ and I thought I’d share it with you. Not that I’m superstitious or anything. I just thought you’d enjoy it.
(...)
Do you need a silencer if you are going to shoot a mime? (That’s my favorite.)
   
Google Books
Cyber Jokes:
The Funniest Stuff on the Internet
By Doug Mayer
Kansas City, MO: Andrews and McMeel
1996
Pg. ?:
Do you need a silencer if you are going to shoot a mime?
       
Google Books
The Mammoth Book of Comic Quotes
Edited by Geoff Tibballs
London, UK: Constable & Robinson Ltd
2004
Pg. ?:
If you wanted to shoot a mime artist, would you use a silencer?
 
Google Books
Do Vegetarians Eat Animal Crackers? and Other Questions You Might Not Think To Ask
By Robert Bimler
Lulu Press (Lulu.com)
2008
Pg. ?:
Do you need a silencer if you are going to shoot a mime?
 
Twitter
Jason Curlee
@JasonCurlee
Do you need a silencer if you are going to shoot a mime?
10:46 PM - 25 Feb 2008
   
Reddit—Shower Thoughts
If you shoot a mime, do you need a silencer?
submitted April 8, 2015 by darthtate
 
Twitter
Funny Jokes
@BarzFunnyJokes
Do you need a silencer if you are going to shoot a mime?
7:50 AM - 4 Feb 2018