An ambassador riddle is:
     
Q: Why do ambassadors never get sick?
A: They have diplomatic immunity.
     
“Why do ambassadors never get sick? Diplomatic immunity” was posted on the newsgroup rec.humor on August 13, 1993.
   
         
Google Groups: rec.humor
List of “Hot Cross Puns”, and more
Harold Reynolds
Aug 13, 1993, 10:10:54 AM
(...)
Why do ambassadors never get sick? Diplomatic immunity.
 
Google Groups: rec.humor
Canonical List Of Language Expressions Humor 3/4
Stuffed Turkey
Nov 23, 1993, 8:51:49 AM
(...)
Why do ambassadors never get sick? Diplomatic immunity.
     
Google Books
April 2000, Boys’ Life, “Think & Grin,” pg. 53, col. 3:
Randy: Why don’t ambassadors ever get sick?
Candy: Why?
Randy: They have diplomatic immunity! — Zack Russ, Darnestown, Md
 
Twitter
PolarCoug
@PolarCoug
Why do ambassadors never get sick? Diplomatic immunity.
3:10 AM · Oct 31, 2009·Twitter Web Client
 
Twitter
Michelle Vasquez
@madtogladdating
Great one liners: Why ambassadors never get sick: diplomatic immunity. #fb
5:47 PM · Oct 21, 2010·Twitter Web Client
       
Reddit—Jokes
Posted by u/bomber96 August 6, 2012
How come ambassadors never get sick?
They have diplomatic immunity
     
Reddit—StupidPuns
Posted by u/SuspiciousTurtle May 31, 2014
Why do ambassadors never get sick?
Diplomatic immunity
 
Reddit—Oneliners
Posted by u/wonliners October 13, 2017
Ambassadors never get sick because they have diplomatic immunity.
     
Google Books
Really Bad Dad Jokes:
More Than 400 Unbearable Groan-Inducing Wisecracks Sure to Make You the Funniest Father With a Quip
By Joe Kerz
New York, NY: Simon & Schuster
2019
Pg. 49:
49.
Why do ambassadors never get sick?
Diplomatic immunity.
 
Reddit—Jokes
Posted by u/InconvenientEase February 23, 2019
Why dont ambassadors get sick?
Diplomatic immunity
 
Twitter
Jimmy RevJim Olsen
@mybuddyjimmy
Why do ambassadors never get sick? Diplomatic immunity. #LaughoftheDay
4:39 PM · Feb 27, 2021 from Urbandale, IA·Twitter for iPhone