Iceberg lettuce has had several “iceberg” jokes. One joke has a patient seeing a doctor:
 
PATIENT: Doctor, I have lettuce sticking out of my bum. Is my condition serious?
DOCTOR: I’m sorry, but it looks like that’s just the tip of the iceberg.
 
The joke—popular in the United Kingdom—has been cited in print since at least 1999.
 
   
Wikipedia: Lettuce
Iceberg/Crisphead – The most popular type in the US, it is very heat-sensitive and was originally adapted for growth in the northern US. It ships well, but is low in flavor and nutritional content, being composed of even more water than other lettuce types.
             
Google Groups: alt.support.ocd
another joke
Dawn Harper
5/12/99
Hi guys,
Just got sent this joke and thought you might like to share.
 
A man goes to the doctor with a piece of lettuce sticking out of his bum.
 
He say to the doctor that he is a little concerned. Upon examination the doctor turns to his patient and says “It’s worse than I originally thought.
 
That’s just the tip of the iceberg”
     
Google Groups: uk.rec.fishing.sea
LETTUCE JOKE
.(JavaScript must be enabled to view this email address)
5/22/99
JUST THOUGHT YOU MIGHT LIKE THIS ONE
A BLOKE GOES TO THE DOCTORS.
WHATS THE PROBLEM SAYS THE DOCTOR.
IT WOULD BE EASIER JUST TO SHOW YOU SAYS THE BLOKE & TAKES DOWN HIS
TROUSERS TO REVEAL A BIT OF LETTUCE STICKING OUT OF HIS ARSE.
WHAT THE HELL IS THAT SAYS THE DOCTOR.
TO WHICH THE BLOKE REPLIES THAT IS THE TIP OF THE ICEBERG.
BARKING MAD SALFORD
   
Google Groups: alt.fan.eddie-izzard
Joke
dt
7/10/99
(...)
heard this one last night ...
 
man goes to the doctor and he has a lettuce sticking out of his arse
“doctor, doctor, tell me what is it ?”
“well i’m not too sure, but i think it may be just the tip of the Iceberg”
   
20 December 2001, Calgary (Alberta) Herald, “Want to hear something funny? Canadians toughest to amuse” by Roger Highfield, pg. A17:
- Britain: A man goes to the doctor and says: “Doctor, there’s a piece of lettuce sticking out of my bottom.” The doctor asks him to drop his trousers and examines him. The man asks: “Is it serious, doctor?” and the doctor replies: “Yes, I’m sorry to tell you that it’s the tip of the iceberg.”
   
Google Books
The Usborne Book of Really Awful Jokes:
About School and Other Stuff
By Laura Howell
Tulsa, OK: EDC Publishing
2005  
Pg. 8:
Nurse, I;ve got lettuce sticking out of my ear.
Oh dear. I fear that it may be just the tip of the iceberg.
 
Google Books
The Mammoth Book of Really Silly Jokes:
Humour for the whole family
Edited by Geoff Tibballs
London: Constable & Robinson Ltd
2011
Pg. ?:
Doctor, Doctor, I’ve got lettuce sticking out of my ear.
Oh dear. I fear that it maybe just the tip of the iceberg.
 
Reddit—Jokes
A man goes to the doctor and says,
submitted August 16, 2013 by rytis
“Doc, there’s a piece of lettuce sticking out of my anus.”
The doctor instructs him to drop his trousers, and then examines him.
The man asks, “Is it serious, doc?”
The doctor replies, “Sorry to tell you, but this is just the tip of the iceberg.”
 
Reddit—Funny
*JOKE* - So a guy goes to his doctor and says, (self.funny)
submitted August 17, 2013 by str0up
“Hey doc, there’s a piece of lettuce sticking out of my anus.”
The doctor instructs him to drop his trousers, and then examines him.
The man asks, “Is it serious, doc?”
The doctor replies, “Sorry to tell you, but this is just the tip of the iceberg.”
 
Reddit—Jokes
A guy goes to a doctor
submitted August 17, 2013 by ElderCunningham
A guy goes to a doctor and says, “Doctor, I don’t know what to do. I woke up this morning, and found a piece of lettuce sticking out of my ass.”
The doctor instructs him to drop his trousers, and then examines him.
The man asks, “Is it serious, doc?”
The doctor replies, “I hate to tell you, but this is just the tip of the iceberg.”
     
Google Books
The Everything Big Book of Jokes:
Hundreds of the Shortest, Longest, Silliest, Smartest, Most Hilarious Jokes You’ve Never Heard!
By Evan C. Thomas
Pg. 171:
A MAN VISITS THE DOCTOR with a head of lettuce sticking out of his ear. The doctor says, “Well I can see your issue right off the bat, Mr. Timmins.”
 
The man replies, “This is just the tip of the iceberg, doc.”
 
Reddit—Jokes
‘Doctor, there’s a piece of lettuce sticking out of my bottom.’
submitted May 11, 2016 by ByronCalloway
The doctor asks him to drop his trousers and examines him.
The man asks: ‘Is it serious, doctor?’ and the doctor replies: ‘I’m sorry to tell you, but this is just the tip of the iceberg.’
   
Twitter
Shit Jokes
@ShitJokes
Man goes to the doctors with a lettuce sticking out of his bum.
“Tell me Doc is it serious?”
Well sir this is just the tip of the iceberg.
7:00 AM - 4 Feb 2017
 
Reddit—3amjokes
“Doctor, I think I have some lettuce sticking out of my bum.” self.3amjokes
Submitted April 1, 2018 by porichoygupto
Doctor: I’m sorry to tell you, but that’s just the tip of the iceberg.
COMMENTS
borrellia
hmmm…lettuce have a look