On St. Patrick's day, a guy gets drunk at a bar and goes to the bathroom to take a piss. When he's done, he looks to his left and sees a tiny man with red hair all dressed in green. Slurring his words, he asks: "Are you a leprechaun?"
The tiny man smiles and says: "Of course I am!"
The drunk smiles and asks: "Do I get your pot of gold, then?"
The leprechaun replies: "Of course you do. But first, you must meet my three challenges."
"Okay. What's the first?"
Pointing to one of the open stalls (they are the only two in the bathroom) the leprechaun explains: "Well, like all leprechauns, I have a huge magical penis. You need to go with me into the bathroom stall and suck on my magic penis until my magical fairy juice erupts from it, which you must swallow."
Excited about getting the pot of gold, the drunk goes into the stall, bends down below the tiny man, unzips his pants, then sucks on his huge penis. After a few minutes of this, the leprechaun shoots a massive amout of white fairy juice in his face. The leprechaun adds: "Be sure to lap it all up."
The drunk does as told, then asks excitedly: "Okay, what's next?"
"Well, like all leprechauns, my magical penis recovers quickly. I need you to pull down your pants so I can stick my huge magical penis into your asshole and fuck it."
The drunk excitedly pulls down his pants and bends over, while the leprechaun jumps on the toilet seat and pulls down his pants. The leprechaun shoves his penis in the drunk's asshole, making him groan, and soon develops a humping motion. The leprechaun smiles, then says: "You're very good at this! Now all you have to do is one little thing."
"What is it?"
"You just need to come up with the answer to my riddle."
"Okay, I'm ready. What's the riddle?"
The tiny man, still humping the drunk, bends over so his lips are next to the drunk's ear, and whispers: "You aren't really dumb enough to believe leprechaun's exist, are you?"