…inspired by the “Randomness” thread…
The funniest things I’ve ever seen scratched on a bathroom wall…
Here I sit all brokenhearted
Tried to shit but only farted
Jesus Saves
and Gretsky scores on the rebound
Don’t look up here, the joke’s in your hand!
Funniest one I saw:
“I banged yer mom good last night”
followed by someone else’s writing-
“You’re drunk dad, go home.”
Another funny one:
Someone originally wrote ‘black power’ but the word ‘black’ was crossed out and the word ‘white’ above it, which in turn was crossed out and the word ‘gay’ above it, which in turn, etc etc.
This wasn’t on a bathroom, it was written in marker on a barrier over a “scenic overlook” on this mountain we visited in PA when I was a kid. It read,
“I killed my boyfriend here
He’s dead
Down there
Somewhere”
And now, a couple of random selections from Penn State Whizdom by Vicki Glembocki and Lynne Smyers, for your enjoyment:
The book is a collection of graffitti found on the bathroom walls at several bars within State College, PA.
“Imagine a world without hypothetical situations.” Zeno’s
“I need something regular in my life other than my period.” Darkhorse
“Why does this gum taste funny?” Den
“Whiskey, whiskey, you’re a pest. You have often kept me from my rest. Often turned my friends to foes. But here you are beneath my nose. So cherrio and down she goes.” Zeno’s
Written near the floor: “If you can read this you’re shitting at an angle.”
I like the obscure ones:
“Heisenberg may have been here.”
“Judge Crater: Call your office.”
Here I sit all brokenhearted
Tried to shit but only farted
Then one day I took a chance
and tried to fart but shit my pants
Check out #88 here. Others may amuse you as well.
My favorite wasn’t written on the stall wall, but on the assgasket dispenser: “Free cowboy hat. Take one!”
Someone wrote in my high school bathroom, “Damn, my shit stinks.” I must have laughed like a loon in that bathroom stall for five minutes. It was particularly funny or clever, it’s just that someone went to the trouble to find a pen and scratch those words into the wall just to share that tidbit with us.
Two from personal experience although not on the wall.
There were normally three sinks in the Men’s room at work. I went in one morning and one of the sinks was removed from its place on the wall and sitting in the middle of the floor. I took out my pen and a paper towel and wrote “Out Of Order” on the towel and put it in the sink on the floor.
Somebody (maintenance I imagine) had put a sign on one of the mirrors in the head to the effect:
Please do not throw paper towels in toilets
And in the proper spirit of displaying the obvious, I put another pen-on-towel notice up beside the one on the mirror which stated:
Please do not shit in the sink
I first read this and had no coffe, soda, milk, water, or any other substance in my mouth with which to spit all over my keyboard or monitor. While I found it to be extremely funny, I was unable to gain the same reaction when I read it again, mouth burning from holding soda. You are, therefore, off the hook with regards to owing me a monitor or keyboard.
I was in a bathroom at college the other day, and was surprised by the amount of times the word cock was written.
I saw, “Towelheads suck cock.” Then, beneath that, “You suck cock.” Beneath that, “You mom sucks my cock.” And so on and so on, repeat ad infinitum.
This is all good stuff! 
We should mention the obligatory For a good time call xxx-xxxx
or For a good BJ, be here date-time. (“Find a happy place! Find a happy place!”)
Not in a bathroom, but while in line to ride on a rollercoaster, I took out my pen and wrote “graffiti” in purple ink on the wooden hand rail.
On one of the walls in a"Red Roof Inns" (just holes in the boards with a roof over head) in Philmont someone had carved:
“I don’t go out with girls anymore,
I live a life of danger,
I sit around and play with myself,
I am a Philmont Ranger.”
Had our entire crew laughing for days.
“MY Mother made me a lesbian”
Underneath is written:
“If I give her the yarn, will she make me on too?”
When I was attending a local college in 1968, I wrote on the grouting in a restroom:
“People who write between the tiles have narrow minds”
The next time I used that stall, I found written below my graffito:
“People who write between the tiles have no minds at all”
Another time I wrote:
“Communismus delendus est”
(“Communism must be destroyed”)
Somebody wrote below that:
“Sic transit gloria feces”
In the restroom of the public library in Hermosa Beach, I once carried some printed stickers.
On the paper-towel dispenser I stuck the one reading “40% water”
On the pipe for the spigot on the urinal I stuck the stiker reading “Hold tight” 
Just last weekend I saw “Jesus est la reponse”. Cracked me up because it was in French. Not sure why that’s so funny. Those French people sure like to get their Jesus on.
Not on a bathroom wall, but on an escarpment along the 401 there is “vote NDP” spray painted in red. It kills me every time I drive by it. Who knew there were politically conscious graffiti artists?
Seen in the men’s room at the National Gallery in London:
Immigrants Out!
Followed by:
**Okay, but that means we’re taking back
Mahatma Gandhi
V.S. Naipaul
Albert Einstein…**
…and it went on for a while; I can’t remember the lengthy list of famous immigrants.