I was once on a 3 day trip in the Everglades. My whole class went, but broke into small co-ed groups, and I wasn't friends with anyone in my group. Anyway, one of the guys in my group started to get a headache and one of the other guys says, "Dude, I have some aspirin in this bag, but it's all crushed up from the trip, you can have some."
The first guy takes it and the other starts laughing, "What? Why are you laughing?"
"That was Viagra."
"Oh sh**, it's working."
The first guy runs off to take care of it, and when he comes back a few minutes later, the second guy is laughing his ass off, "Dude, I was joking, it was actually aspirin."
Earlier that day, the first guy from the story above is in the porta-potti thing on the little island thing we stopped out canoes at to camp on, and he's peeing, and the rest of us are waiting out turn, one of the guys just runs into the side of the thing. The wobbles WAY off to the side and we all here this horrible splashing sound followed shortly by, "OH MY GOD!!!!!!!!!!"
It was hilarious, and I was oh so glad it wasn't me. XD