Skunk, Dog Crap and Ketchup - S8-E13
Factual error: Despite Alan's general bad luck he indeed wouldn't have to be afraid of the skunks. In reality skunks use their anal scent glands very reluctantly and only if they feel threatened because they only carry a limited amount of liquid and have a rather long "recharging" time. To that effect a skunk that apparently feels home in a suburban surrounding would never feel threatened by a human.
Answer: That would be "Corey's Been Dead For an Hour" in season 4, episode 9.
Super Grover ★