“A guy walks into a bar…” is a typical form of what has been called the “bar joke.” A spark plug version is:
 
“A spark plug walks into a bar. The bartender says, ‘I’ll serve you, but don’t start anything.’”
 
The joke has been cited in print since at least 2009. “A jumper cable walks into a bar…” is the same joke.
 
     
Twitter
IG: PRISCILLARENEA‏
@PriscillaRenea
A spark plug walks into a bar and says “Gimmie a beer!” The bartender looked at him and said “Okay, but don’t you start anything!!!”
7:20 PM - 12 Aug 2009
 
Twitter
Arnold Bleicher‏
@OregonGuy
Spark plug walks into a bar & says “give me a beer.” Bartender looks at the spark plug and says, “well, OK, but don’t start anything.”
10:35 AM - 20 Sep 2009
 
Twitter
Kristian Cardillo‏
@kcardillo84
A spark plug walks into a bar and orders a beer. The bartender says, “I’ll serve you but don’t start anything.”
1:33 PM - 27 Nov 2009
   
Twitter
Ellen Byrne‏
@ellenbyrne
A spark plug walks into a bar and orders a whiskey. The bartender says “okay, but you’d better not try to start anything!”
4:33 PM - 9 Apr 2010
   
Twitter
Matt Nunn‏
@MattNunn2
A jump lead and a spark plug walk into a bar…
Barman says “I’ll serve ya, but don’t start anything”
3:58 PM - 11 Nov 2016
 
Reddit—Jokes
A spark plug walks into a bar…
submitted January 16, 2018 by pablosnazzy
Bartender says “I’ll serve you, but don’t start anything.”