Skunked

S2, E27: Mordecai and Rigby are picking up dead animals as a chore when suddenly they discover a skunk lying around. At first they believe they are finally finished as the skunk appears to be dead only to realise that it's actually alive. To make matters worse this skunk turns out to be an angry were-skunk who sprays Rigby with his stench. Now Mordecai and Rigby must find a cure before Rigby completely transforms into a were-skunk