A popular joke has been told about lawyers since at least 1993:
 
Q: What’s the difference between a lawyer and a sperm?
A; A sperm has a one-in-a-million chance of becoming a human being.
 
Another form of the joke was also cited in 1993:
 
Q: What do sperm and a lawyer have in common?
A: They both have a one in a million chance of becoming a human being.
 
     
Google Books
U.S. News & World Report
Volume 115, Issues 1-9
1993
Pg. ?:
What’s the difference between a lawyer and a sperm? The sperm has a l-in-100 million chance of becoming human. The American Bar Association isn’t laughing.
   
Google Books
Sing Out
1993
Pg. 66:
By the way, what do a politician and a sperm cell have in common? They each have a one-in-a-million chance of becoming a human being.
 
Google Groups: rec.humor
Multiple choice
Ken Kaufman
1/6/93
What’s the difference between a lawyer and a sperm?
a) A sperm has a one-in-a-million chance of becoming a human being.
b) Atlanta would never dream of having a giant blue lawyer as its olympic mascot.
 
20 May 1993, Syracuse (NY) Herald-Journal, “le Joke,” pg. D2, col. 4:
What do sperm and a lawyer have in common? They both have a one in a million chance of becoming a human being.
 
Google Books
Ultimate Risk
By Adam Raphael
London: Bantam Press
1994
Pg. 117:
‘What’s the difference between a single sperm and a lawyer?’ Answer: ‘The sperm has one-in-a-million chance of becoming a human being.’
 
Google Books
Law V. Life: What Lawyers are Afraid to Say about the Legal Profession
By Walt Bachman
Rhinebeck, NY: Four Directions Press
1995
Pg. 86:
Q. What do a lawyer and a sperm cell have in common?
A. Each has a one-in-a-million chance of becoming a human being.
 
Google Books
Lowering the Bar:
Lawyer Jokes and Legal Culture
By Marc Galanter
Madison, WI: The University of Wisconsin Press
2005
Pg. 203:
What do lawyers and sperm have in common?
Only one in three million does any real work.
Or
There’s always more than you’d ever need.
Or
Each has a one-in-a-million chance of becoming a human being.
 
Google Books
Ill-Legal Justice:
Baptism of a Deadbeat Dad
By Pete Becich
Xlibris Corporation (Xlibris.com)
2011
Pg. 55:
Joke: What is the difference between a lawyer and a sperm cell? The sperm cell has a one-in-a-million chance of becoming a human being!