The Evils of Marijuana

A certain college professor was notorious for getting off the topic of the lecture, and on to his favorite subject: the evils of marijuana.  Off he went one day into his inventory of horrors, "Used regularly," he explained, "pot can cause psychic disorientation, sterility, cancer and castration!"
"Now wait a minute, professor," interrupted a student. "Castration?  That's absurd!"
"Yes young man, it's sadly true." replied the professor smugly.  "Just suppose your girlfriend gets the munchies!"

Prime Weed

Q: What do prime numbers and stoners have in common?
A: The higher they are, the more spaced out they get.

Smart Alec

A stoner stumbles out of a party, and starts to walk home.
One the way he bumps into a guy who is all bloody and mangled. The guy limps up to the stoner and says "Call me an ambulance!" The stoner looks at him for a second, smiles and says, "You're an ambulance!"